Add restoreCacheV2 tests

[Link-]

• https://github.com/github/actions-relaunch/issues/1026
• Integrate cache service v2 #1857

This is a continuation of the work to integrate toolkit/cache with cache service v2. The bulk of this PR is adding unit tests to restoreCacheV2.

Notable changes

Improvements to logging and debugging:

• packages/cache/src/cache.ts: Added a debug log to display the cache service version in the restoreCache function.

Refinements to error handling:

• packages/cache/src/cache.ts: Updated the restoreCacheV2 function to suppress non-validation errors and return undefined when an error occurs. [1] [2]
• packages/cache/src/cache.ts: Modified the saveCacheV2 function to handle ReserveCacheError separately and log an info message instead of a warning.

Function signature update:

• packages/cache/src/internal/blob/download-cache.ts: Changed the return type of the downloadCacheFile function to Promise<BlobDownloadResponseParsed>.