fix(vscode): cap and chunk file search initialization to prevent event loop starvation (#13249)

[maoxin1234]

Description

Fixes #13249.

On large or Remote-SSH workspaces, \FileSearch.initializeFileSearchState()\ previously walked and indexed every file into MiniSearch in a single synchronous call with no cap. This blocked the Node.js event loop in the extension host for dozens of seconds, leading to connection timeouts and renderer crashes on remote workspaces.

Changes

1. Added \MAX_FILE_SEARCH_FILES = 50_000\ cap to prevent unbounded in-memory index growth.
2. Added \FILE_SEARCH_BATCH_SIZE = 1_000\ chunking to \initializeFileSearchState().
3. Yielded to the event loop (\�wait new Promise((resolve) => setTimeout(resolve, 0))) between batches so the extension host and remote connection handlers stay responsive.

Test Plan

• Verified source builds and unit tests pass.