Refactor keyrange

[lxl66566]

close #743

Please briefly answer these questions:

• what problem are you trying to solve? (or if there's no problem, what's the motivation for this change?)

  • Previously we always transformed between KeyRange and Interval<BytesAffine>, transform through &[u8]. This may make unnecessary Vec clone and memory allocation.
  • And the conflict check in KeyRange is too confusing and troubling due to Bounds.

• what changes does this pull request make?

  • now KeyRange is refactored:

    pub enum KeyRange {
        OneKey(Vec<u8>),
        Range(Interval<BytesAffine>),
    }

    and it can convert between EtcdKeyRange and Interval<BytesAffine> without cloning.
  • The conflict check is also convenient by using Interval::overlap.
  • The reason spliting KeyRange to OneKey and Range is to distinguish prefix and onekey, which may has same form in [a, a+1).
  • refactored some KeyRange usage in crates/xline/src/storage/index.rs and crates/xline/src/storage/kv_store.rs. By using KeyRange directly instead of start: &[u8], end: &[u8] maybe better to construct from one key or all keys, and reduce the clone times.

• are there any non-obvious implications of these changes? (does it break compatibility with previous versions, etc)

[mergify]

@lxl66566 Convert your pr to draft since CI failed

[codecov]

Codecov Report

Attention: Patch coverage is 78.69955% with 95 lines in your changes missing coverage. Please review.

Project coverage is 75.20%. Comparing base (e35b35a) to head (75cda98).
Report is 321 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/xlineapi/src/keyrange.rs	75.72%	66 Missing and 9 partials ⚠️
crates/xline/src/storage/index.rs	75.51%	12 Missing ⚠️
crates/xlineapi/src/lib.rs	63.63%	4 Missing ⚠️
crates/xline/src/storage/kv_store.rs	96.29%	1 Missing and 1 partial ⚠️
crates/xline/src/storage/auth_store/perms.rs	80.00%	1 Missing ⚠️
crates/xline/src/storage/lease_store/mod.rs	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #939      +/-   ##
==========================================
- Coverage   75.55%   75.20%   -0.36%     
==========================================
  Files         180      190      +10     
  Lines       26938    28625    +1687     
  Branches    26938    28625    +1687     
==========================================
+ Hits        20353    21526    +1173     
- Misses       5366     5791     +425     
- Partials     1219     1308      +89     

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[mergify]

@lxl66566 Your PR is in conflict and cannot be merged.

[github-actions]

This PR is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 14 days

[mergify]

@lxl66566 Convert your pr to draft since CI failed

[bsbds]

A single key is ["a", "a\x00") while a prefix should be ["a", "b"). Why do we need a separate OneKey variant?

[bsbds]

Would it be more appropriate to name it Successor?