feat: add a default internal schema

[sunng87]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

Fixes #2964

This patch introduces a new built-in default schema as namespace of tables created by greptime applications. We have more information discussed in #2964 . In most cases, I think our user won't need to know about this schema.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bd9c2f2) 84.78% compared to head (b01862b) 85.37%.
Report is 108 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2974      +/-   ##
===========================================
+ Coverage    84.78%   85.37%   +0.58%     
===========================================
  Files          734      777      +43     
  Lines       114927   124930   +10003     
===========================================
+ Hits         97440   106655    +9215     
- Misses       17487    18275     +788     

[waynexia]

Do we need to register this schema on metasrv? Others looks good to me

[sunng87]

@waynexia If I understand correctly it should be done here: https://github.com/GreptimeTeam/greptimedb/pull/2974/files#diff-44b4862dfce3f3bb50a4845cd5bc075169fa40e0a678ff23ed9816c59c62ac06R308

[killme2008]

@waynexia If I understand correctly it should be done here: https://github.com/GreptimeTeam/greptimedb/pull/2974/files#diff-44b4862dfce3f3bb50a4845cd5bc075169fa40e0a678ff23ed9816c59c62ac06R308

@WenyXu @fengjiachun Please take a look

[WenyXu]

Do we need to register this schema on metasrv? Others looks good to me

Yes, it does. BTW, there is some future work that registering schema should be executed only on the metasrv leader.

[fengjiachun]

LGTM