Add support for Query Hints for MS Fabric in TSql170Parser (#180)

[NAVEEN NAIK (ZEUSXXIV)]

Description

Fixes#180.

Adds support for MS Fabric query hints (FOR TIMESTAMP AS OF '<literal>', FORCE SINGLE NODE PLAN, and FORCE DISTRIBUTED PLAN) in TSql170Parser, TSql180Parser, and TSqlFabricDWParser. These hints are mapped to AST enums (ForceSingleNodePlan, ForceDistributedPlan, ForTimestampAsOf) and handled appropriately in the T-SQL parser grammar and script generator visitor. Includes new regression unit test coverage.

Code Changes

• Unit tests are added, if possible
• Existing tests are passing
• New or updated code follows the guidelines here

[Leila Lali (llali)]

M1 — Positive-only test coverage; no negative / version-gating assertions.
FabricQueryHints170.sql only exercises the happy path. The repo's testing guidelines call for negative coverage. Because older versions are null (ignored), the test also doesn't lock in that pre-170 parsers reject this syntax. Recommend adding a negative case to ParserErrorsTests.cs (e.g. FORCE SINGLE PLAN missing NODE, or FOR TIMESTAMP AS OF without a string literal) and/or an nErrors160: 1 assertion to pin version gating.

[Leila Lali (llali)]

please add negative tests. everything else look good

[NAVEEN NAIK (ZEUSXXIV)]

Leila Lali (@llali) Ah yes! I missed out on adding the negative test cases, I have updated the PR accordingly.