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)

[jiacai2050]

We should avoid create new Vec in write path, it will hurt perf.

[jiacai2050]

We should do this in MetricManager module.

[jiacai2050]

For index cache manager, it will only cache series, metrics will be managed be metrics manager.

In this way, our code is more modular.

[jiacai2050]

Two thoughts here:

1. We should prefer std map over dash map, those third party may introduce unexpected bugs.
2. For current segment cache, we can use an independent field to represent, so we can save one hashmap lookup.

Other questions we need to consider:

1. How will you evict segment?

[jiacai2050]

The cache module shouldn't known how the persistence layer is implemented, we can move this method to IndexManager.

[jiacai2050]

Cache module has no schema, this field belong to IndexManager.