Add Parquet caching for DataFusion metrics scans

[alexanderbianchi]

Summary

Adds Parquet IO caching for DataFusion metrics scans.

This PR includes the footer metadata cache work from #6388 and the follow-up DataFusion-local parquet byte-range cache:

• installs DataFusion's CachedParquetFileReaderFactory for parquet footer metadata reuse;
• adds a DataFusion object-store cache path backed by Quickwit's in-memory MemorySizedCache;
• scopes cache keys by storage URI so equivalent object paths in different buckets/authorities do not collide;
• keeps DataFusion cache sizing behind the datafusion serve setup with a 4 GiB default and QW_DATAFUSION_PARQUET_RANGE_CACHE_CAPACITY override;
• documents the path to a future Foyer-backed block/range cache in docs/internals/parquet-byte-range-cache-option2.md.

Validation

• cargo check -p quickwit-serve --features datafusion
• cargo test -p quickwit-datafusion
• cargo test -p quickwit-storage --features testsuite
• cargo check -p quickwit-lambda-server
• git diff --check