fix(sqla): allow 'unknown' type queries in explore view

[serenajiang]

SUMMARY

After we deployed #11236, several charts broke because the sql parser could not identify the type of the query and pessimistically classified them as write queries. These problems occur because the sql parser is sensitive to certain syntax issues that may not actually be problems in some dialects of sql (in this case, presto sql).

These errors are confusing to users because their queries work in sql lab but fail in explore view. Debugging and fixing the so-called "incorrect" syntax is very tedious.

In this PR, I am allowing queries with an "UNKNOWN" type (optimistic instead of pessimistic). This couuuuld potentially allow some write queries through, but it's still a step up from how things were before #11236.

TEST PLAN

Some examples of correct queries that failed in explore view due to unknown type:

WITH x AS(SELECT 1 AS col) SELECT * FROM x

WITH events AS (SELECT 1 AS col) SELECT * FROM events

ADDITIONAL INFORMATION

• Has associated issue: Superset chart incorrectly throwing error Virtual dataset query must be read-only #11310
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[villebro]

Thanks @serenajiang for the fix, apologies for the inconvenience!

[villebro]

Btw, I'm surprised sqlparse is not able to identify regular CTEs as read only. Will potentially take a stab at adding that to the library.

[codecov-io]

Codecov Report

Merging #11365 into master will decrease coverage by 9.55%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #11365      +/-   ##
==========================================
- Coverage   65.75%   56.20%   -9.56%     
==========================================
  Files         838      406     -432     
  Lines       39716    13564   -26152     
  Branches     3615     3443     -172     
==========================================
- Hits        26116     7623   -18493     
+ Misses      13499     5771    -7728     
- Partials      101      170      +69     

Flag	Coverage Δ
#cypress	56.20% <ø> (-0.21%)	⬇️
#javascript	?
#python	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...uperset-frontend/src/dashboard/util/dnd-reorder.js	0.00% <0.00%> (-100.00%)	⬇️
...rset-frontend/src/dashboard/util/getEmptyLayout.js	0.00% <0.00%> (-100.00%)	⬇️
...et-frontend/src/components/Menu/LanguagePicker.tsx	0.00% <0.00%> (-100.00%)	⬇️
...dashboard/components/resizable/ResizableHandle.jsx	0.00% <0.00%> (-100.00%)	⬇️
...d/src/views/CRUD/csstemplates/CssTemplatesList.tsx	2.43% <0.00%> (-94.86%)	⬇️
.../src/dashboard/util/getFilterScopeFromNodesTree.js	0.00% <0.00%> (-93.48%)	⬇️
...uperset-frontend/src/utils/getClientErrorObject.ts	0.00% <0.00%> (-89.19%)	⬇️
.../src/dashboard/components/FilterIndicatorGroup.jsx	11.76% <0.00%> (-88.24%)	⬇️
...c/explore/components/controls/withVerification.jsx	9.09% <0.00%> (-87.88%)	⬇️
...src/dashboard/components/gridComponents/Header.jsx	10.52% <0.00%> (-86.85%)	⬇️
... and 652 more

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