feat(mito): Init the write cache in datanode

[evenyag]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

This PR initializes the WriteCache according to the mito config. By default, the write cache is under DATA_HOME/write_cache and is disabled.

It addresses an issue that the file cache doesn't use get() to access cache entries.

It also refactors some mods to make the integration easier

• Adds a builder for the CacheManager
• Recovers the FileCache in WriteCache::new
• MitoEngine::new is an async function now
• Provides a util to attach layers to ObjectStore

Now write cache is still an experimental feature so I added prefixes to its config items.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

Refer to a related PR or issue link (optional)

• mito: Write cache for remote object store #2965

[codecov]

Codecov Report

Attention: 70 lines in your changes are missing coverage. Please review.

Comparison is base (e0a43f3) 85.66% compared to head (ea008e4) 85.19%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3100      +/-   ##
==========================================
- Coverage   85.66%   85.19%   -0.48%     
==========================================
  Files         807      807              
  Lines      132167   132354     +187     
==========================================
- Hits       113227   112755     -472     
- Misses      18940    19599     +659     

[QuenKar]

LGTM