feat: metadata cache core impl

[hiltontj]

Part of #25543

Implement the base MetaCache type that holds the hierarchical structure of the metadata cache providing methods to:

• create the cache (here),
• push rows from the WAL into the cache (here),
• get record batches out of the cache with a given set of predicates (here), and
• prune the cache based on a max_age and a max_cardinality (here)

Tests

• Verify predicate evaluation when fetching record batches from the cache (here)
• Verify pruning of the cache (here)

Notes

• This PR adds a influxdb3_cache crate, which just holds the metadata cache for now, but may well also hold the last-n-value cache and parquet cache to get those out of the influxdb3_write crate
• Some accessory changes were made, namely, to expose the WriteValidator from influxdb3_write so it can be used as a more light-weight way of parsing line protocol and producing Rows for tests
• To close the related issue, I still need to add a MetaCacheProvider and other pieces necessary to tie this into the system.

[hiltontj]

@alamb I tagged you on this as it is using StringView and I thought that may interest you. Starting here: https://github.com/influxdata/influxdb/blob/dff0b2ec913a0599ee7b9404f814bbc1807cea6f/influxdb3_cache/src/meta_cache/mod.rs#L183-L220