fix(mcp): add AliasChoices to chart/dashboard/dataset request schemas

[aminghadersohi]

Summary

• LLM-driven MCP callers commonly send field name variants like id instead of identifier, or columns instead of select_columns. Pydantic silently drops unrecognized keys and falls back to field defaults, so these requests behaved as if the field was never sent at all.
• Adds validation_alias=AliasChoices(...) plus model_config = ConfigDict(populate_by_name=True) to the chart, dashboard, and dataset MCP request schemas that were missing them, following the existing pattern already used by OpenSqlLabRequest and GenerateDashboardRequest.
• Affected schemas: GetChartInfoRequest, ListChartsRequest, GenerateExploreLinkRequest, UpdateChartRequest, UpdateChartPreviewRequest, GetChartDataRequest, GetChartPreviewRequest, GetChartSqlRequest, ListDashboardsRequest, GetDashboardInfoRequest, AddChartToDashboardRequest, ListDatasetsRequest, GetDatasetInfoRequest.

Test plan

• ruff format / ruff check clean on all changed files
• mypy and pylint pre-commit hooks pass on all changed files
• Added unit tests covering each new alias (id/chart_id/dashboard_id/dataset_id → identifier, columns → select_columns, dashboard/chart → dashboard_id/chart_id) in test_chart_schemas.py, test_dashboard_schemas.py, and a new test_dataset_schemas.py
• CI test suite (could not run the full pytest suite locally — mysqlclient failed to build in this sandbox due to missing native libs)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.42%. Comparing base (fd9c84b) to head (990c4c7).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #41597      +/-   ##
==========================================
- Coverage   64.42%   64.42%   -0.01%     
==========================================
  Files        2668     2668              
  Lines      147182   147194      +12     
  Branches    33947    33947              
==========================================
+ Hits        94821    94828       +7     
- Misses      50646    50649       +3     
- Partials     1715     1717       +2     

Flag	Coverage Δ
hive	39.11% <100.00%> (+0.01%)	⬆️
mysql	57.66% <100.00%> (+<0.01%)	⬆️
postgres	57.72% <100.00%> (+<0.01%)	⬆️
presto	40.66% <100.00%> (+0.01%)	⬆️
python	59.13% <100.00%> (+<0.01%)	⬆️
sqlite	57.36% <100.00%> (+<0.01%)	⬆️
unit	100.00% <ø> (ø)

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