YDB-3472: Support StrictSerializableRW and commit timestamps in PHP Query Service

[vgvoleg]

Adds Query Service access through Ydb::queryService() with StrictSerializableRW transaction settings and explicit session and transaction IDs. Exposes optional commit timestamps from explicit commits and the final ExecuteQuery response part as CommitTimestamp values, with access to the original Ydb.VirtualTimestamp protobuf.

Timestamp comparison uses unsigned plan_step and tx_id and accepts values only from the same Ydb connection object. The protobuf has no database identity, so timestamps from separate connections remain incomparable even when their configured paths match. The pinned ydb-api-protos revision already contains the required fields and matches current upstream.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.36%. Comparing base (95214df) to head (e92683e).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #299      +/-   ##
============================================
+ Coverage     52.67%   55.36%   +2.69%     
- Complexity      989     1054      +65     
============================================
  Files            66       69       +3     
  Lines          2690     2841     +151     
============================================
+ Hits           1417     1573     +156     
+ Misses         1273     1268       -5     

Components	Coverage Δ
Native SDK	55.36% <100.00%> (+2.69%)	⬆️

Files with missing lines	Coverage Δ
src/CommitTimestamp.php	100.00% <100.00%> (ø)
src/QueryExecutionResult.php	100.00% <100.00%> (ø)
src/QueryService.php	100.00% <100.00%> (ø)
src/Ydb.php	76.27% <100.00%> (+0.83%)	⬆️

... and 2 files with indirect coverage changes

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[Copilot]

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[Copilot]

Copilot review overview

🟡 Changes recommended

Error recovery can mask failures or invalidate sessions, and timestamp parsing uses an undeclared extension.

Review effort: Balanced
Findings: 1 · 2

Open (3)

• Avoid undeclared ctype dependency for timestamp validation · New
• Rediscover only for transport-related gRPC statuses · New
• Catch Throwable during endpoint rediscovery · New

[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation matches the described API and includes comprehensive coverage of its critical behavior.

Review effort: Balanced
Findings: None

Resolved since last review (3)

• Avoid undeclared ctype dependency for timestamp validation
• Catch Throwable during endpoint rediscovery
• Rediscover only for transport-related gRPC statuses