Add optional DocumentSymbol tooltip support in outline and breadcrumbs

[Copilot]

Document symbols in outline/breadcrumbs were effectively constrained to name/detail, with breadcrumbs not surfacing richer context. This change adds an explicit symbol tooltip channel and threads it through API conversion and UI rendering so hover text can carry meaningful symbol context.

• API/model surface

  • Added optional tooltip?: string to DocumentSymbol across core/internal/API typings:
    • src/vs/editor/common/languages.ts
    • src/vs/monaco.d.ts
    • src/vscode-dts/vscode.d.ts
    • src/vs/workbench/api/common/extHostTypes.ts

• Ext host conversion + command results

  • Preserved tooltip through document symbol converters in extHostTypeConverters.
  • Included tooltip in vscode.executeDocumentSymbolProvider merged document-symbol results in extHostApiCommands.

• Outline + breadcrumbs hover behavior

  • Updated symbol label title generation to prefer provider-supplied tooltip, with existing fallback retained:
    • src/vs/workbench/contrib/codeEditor/browser/outline/documentSymbolsTree.ts

title: element.symbol.tooltip
	?? localize('title.template', "{0} ({1})", element.symbol.name, symbolKindNames[element.symbol.kind])

• Coverage update
  • Extended existing document symbol command test to assert tooltip propagation for root and child symbols.