fix(mssql): update SQL keywords to uppercase for consistency

[mattiasthalen]

This pull request updates SQL queries in the MSSQL engine adapter and its corresponding tests to use uppercase identifiers for schema objects (INFORMATION_SCHEMA, TABLES, COLUMNS, etc.) to align with SQL standards and improve consistency. The changes span both the core implementation and the test suite.

NOTE: This is done to enable the fabric engine adaptor without having to override functions from the MSSQL engine adaptor.

Core MSSQL Engine Updates:

• Updated columns method in sqlmesh/core/engine_adapter/mssql.py to use uppercase identifiers for schema objects (COLUMN_NAME, DATA_TYPE, etc.) and table-related keywords (TABLE_NAME, TABLE_SCHEMA).
• Updated table_exists method in sqlmesh/core/engine_adapter/mssql.py to use uppercase identifiers for INFORMATION_SCHEMA.TABLES and table-related keywords (TABLE_NAME, TABLE_SCHEMA).

Test Updates for MSSQL Engine:

• Adjusted SQL queries in tests/core/engine_adapter/test_mssql.py to match the updated uppercase schema object identifiers in tests for columns, table_exists, and various table operations such as CREATE TABLE, MERGE, and INSERT.