Fix batchInsert() crash on array values for JSON columns

[WarLikeLaux]

Q	A
Is bugfix?	✅
New feature?	❌
Breaks BC?	❌
Fixed issues	#20683

What does this PR do?

Fixes batchInsert() crash ("Array to string conversion") when inserting PHP arrays into JSON columns. Alternative to #20684.

Problem

batchInsert() wraps arrays in JsonExpression via dbTypecast() only when table schema is found. When schema is unavailable (table name with {{%}} notation, missing table, etc.), raw arrays pass through all type checks and hit implode(), causing a PHP warning.

Fix

1. Added base JsonExpressionBuilder in yii\db - default builder for backends without a vendor-specific one (SQLite, MSSQL, Oracle, CUBRID). MySQL and PostgreSQL keep their own.
2. Registered it in QueryBuilder::defaultExpressionBuilders().
3. Added is_array() fallback in batchInsert() across 3 QueryBuilder implementations (base, pgsql, oci) - wraps raw arrays in JsonExpression and processes via buildExpression().

Uses parameter binding (:qp0 placeholders) instead of inline json_encode(), which prevents SQL injection.

Tests

QueryBuilderTest (2) - array value with param binding, JsonExpression with Query subquery

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.58%. Comparing base (379b296) to head (5e54dc3).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #20768      +/-   ##
============================================
+ Coverage     78.56%   78.58%   +0.01%     
- Complexity    11568    11573       +5     
============================================
  Files           376      377       +1     
  Lines         30750    30763      +13     
============================================
+ Hits          24160    24174      +14     
+ Misses         6590     6589       -1     

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