Deprecate AbstractSchemaManager::getSchemaSearchPaths()

[morozov]

Q	A
Type	deprecation
BC Break	no

The concept of a search path as well as the "public" schema name are specific to PostgreSQL and don't belong to the DBAL:

dbal/src/Schema/Schema.php

Line 76 in 3f45d98

$this->_setName($schemaConfig->getName() ?? 'public');

The APIs around the search path are only used by the PostgreSQL schema manager and only in order to identify the current schema (which is the first element of the search path). The protected PostgreSQLSchemaManager::getCurrentSchema() method is being introduced for this purpose.

TODO:

• Rebase after merging the changes from Fix Schema::getTableNames() #4811 into 3.2.x (Merge 3.1.x into 3.2.x #4820).