Refactoring the persistence layer to be able to persist any Java Object

[yojs]

Fixes #: #399

Description of changes:

The persistence layer takes care of durably storing the RCA results (and in future decisions from deciders) and providing them when asked for it. The layer also takes care of periodic file rotations and cleaning up old DB files.

Although, it wasn't intended, the Persistence layer is tightly coupled with the RCA graph today. If you look at the write() method in Persistable interface, you will find this signature:
<T extends ResourceFlowUnit> void write(Node<?> node, T flowUnit) throws SQLException, IOException;

So the Persistable Object knows about the graph node. Therefore, in future as the remediation system evolves and we have components, that are not nodes in the RCA-Graph, we might still want to persist their outputs. But this interface can't do that.

Therefore, the goal is to make the methods of Persistable generic, so that it can persist any object given to it and be able to read out any object the caller asks for.

Say we have to persist this class:

Outer.java
________________

class Outer {
  int x;
  int y;
  boolean z;
  String name;
  List<T> myList;
  B b_obj;
}
-------------------------------------------------------

A.java
_______

class B {
  int x;
  String y;
}

when the above code is annotated as:

Outer.java
________________

// This will create a table named "Outer"
class Outer {
  @ValueColumn
  int x;

  @ValueColumn
  int y;
  // Its not annotated as column, therefore, it will not be persisted.
  boolean z;

  @ValueColumn
  String name;

  @RefColumn
  B b_obj;

  @RefColumn
  List<T> myList;

  // Add a column named x to Outer table. The value stored in the row for that column will be the value of x.
  int getX() { .. }
  void setX(int x) { .. }

  int getY() { .. }
  String getName() { .. }
  void setName(String name) { .. }

  // For all fields that are not [primitive types](https://docs.oracle.com/javase/6/docs/api/java/lang/Class.html#isPrimitive()), they will be persisted in their own tables as a new row. The auto-increment ID
for this row will be persisted as a value of the column named "__table__B", so that we have a link to the nested element/table from this table.
  B getBObj() {..}
  void setBObj(B b) {..}

// If the Column annotation exists for a collection type, then they will be written to a table of their own. 
// The name of the table is obtained by calling T.class.getSimpleName(). If all of them evaluates to the same 
// table name, then they get written to the same table as different rows. And the corresponding Outer table's
// column will have a string [<rowId1]>, <rowId2>].
// If `T.class.getSimpleName()` evaluates to different names, then they are linked back in Outer table as 
// different columns.
  List<T> getMyList() { .. }
  void setMyList(List<T> list) { .. }
}
-------------------------------------------------------

B.java
_______

class B {
  @ValueColumn
  int x;
  String y;

  int getX() { .. }
  void setX(int x) { .. }
}

this creates these set of tables:
Here assuming that

getMyList() returns a list of three elements where

for (T in getMyList) {
  // T.getClass().getSimpleName() returns `T` for two of the objects and `TT` for the third.
}

Table Outer

ID	X	Y	Name	__table__BObj	__table__T	__table__TT
53	1	2	name	34	[{"tableName":"ITestImpl2","rowIds":[1]},{"tableName":"ITestImpl1","rowIds":[1,2]}]	32

Table B

ID	X
34	23

Table T

ID	col2	..
23	24	..
24	24	..

Table TT

ID	col2	..
32	24	..

What this buys us

• The Java code resembles how the tables and nested tables will be laid out.
• Because the nested table can be obtained just by reading the column name, someone can write a tool to read the RCAs from the SQLite files. The won't need the java package to figure out the nesting.
• If new columns or nestings are added, they can also be added in the DB without schema mismatch. This is because, we create a new SQLite file on each restart of the RCA agent process (on top of periodic file rotations).
• The table name and column names are derived from the classname and getter name (methodName with get stripped out). This provides a 1-1 mapping from the persistor class and fields to the table name and column names.
• Over and above, we are able to persist any Java Object.

Tests:
Added unit tests

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #407 into master will increase coverage by 0.70%.
The diff coverage is 82.97%.

@@             Coverage Diff              @@
##             master     #407      +/-   ##
============================================
+ Coverage     70.09%   70.80%   +0.70%     
- Complexity     2287     2354      +67     
============================================
  Files           303      307       +4     
  Lines         13605    13962     +357     
  Branches       1133     1178      +45     
============================================
+ Hits           9537     9886     +349     
- Misses         3695     3702       +7     
- Partials        373      374       +1     

Impacted Files	Coverage Δ	Complexity Δ
...ormanceanalyzer/rca/persistence/PersistorBase.java	78.50% <46.66%> (-5.20%)	23.00 <1.00> (+1.00)	⬇️
...manceanalyzer/rca/persistence/SQLitePersistor.java	77.21% <85.05%> (+8.70%)	72.00 <44.00> (+44.00)
...ormanceanalyzer/rca/store/rca/cache/CacheUtil.java	58.62% <0.00%> (ø)	9.00% <0.00%> (ø%)
...performanceanalyzer/rca/framework/core/Config.java	100.00% <0.00%> (ø)	7.00% <0.00%> (?%)
...cisionmaker/actions/configs/CacheActionConfig.java	100.00% <0.00%> (ø)	5.00% <0.00%> (?%)
...cisionmaker/actions/configs/QueueActionConfig.java	97.22% <0.00%> (ø)	5.00% <0.00%> (?%)
...manceanalyzer/rca/framework/core/NestedConfig.java	100.00% <0.00%> (ø)	5.00% <0.00%> (?%)
...ceanalyzer/rca/framework/core/ConfJsonWrapper.java	94.59% <0.00%> (+0.30%)	20.00% <0.00%> (+4.00%)
...performanceanalyzer/rca/configs/DeciderConfig.java	47.05% <0.00%> (+0.39%)	4.00% <0.00%> (-4.00%)	⬆️
...erformanceanalyzer/rca/framework/core/RcaConf.java	52.21% <0.00%> (+1.30%)	33.00% <0.00%> (+2.00%)
... and 6 more

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[yojs]

The failed test is Test testFieldDataCacheRca FAILED is a known issue