fix: lease keys in conflict pool

[bsbds]

Depends-On: #852

Fix lease related logic in conflict pools.

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?)

• what changes does this pull request make?

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 94.94949% with 20 lines in your changes missing coverage. Please review.

Project coverage is 75.78%. Comparing base (e35b35a) to head (3d109cb). Report is 132 commits behind head on master.

Files	Patch %	Lines
crates/xline/src/conflict/tests.rs	94.84%	0 Missing and 10 partials :warning:
crates/xline/src/conflict/spec_pool.rs	88.88%	4 Missing :warning:
crates/curp/src/server/conflict/mod.rs	50.00%	3 Missing :warning:
crates/xline/src/conflict/uncommitted_pool.rs	93.93%	2 Missing :warning:
crates/xlineapi/src/lib.rs	97.14%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #861 +/- ## ========================================== + Coverage 75.55% 75.78% +0.23% ========================================== Files 180 188 +8 Lines 26938 28045 +1107 Branches 26938 28045 +1107 ========================================== + Hits 20353 21255 +902 - Misses 5366 5488 +122 - Partials 1219 1302 +83 ```

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