feat: metrics engine cache

[zealchen]

Rationale

#1623

Detailed Changes

1. Sequence diagram

2. Implement three caches: MetricsCache, SeriesCache, and TagIndexCache, each with an asynchronous serialization function.

3. Implement async write to storage in batch mode.

TODO:

1. Some parameters need to be made configurable.

Test Plan

UT

running 1 test
test index::cache::tests::test_cache_manager_updates ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 3.05s

     Running unittests src/lib.rs (target/debug/deps/pb_types-2fb383c00286addd)