feat: Speculative Pool WAL

[bsbds]

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?)

  Implements write-ahead-log for speculative pool

• 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 86.98092% with 116 lines in your changes are missing coverage. Please review.

Project coverage is 75.99%. Comparing base (e35b35a) to head (efa63a3). Report is 83 commits behind head on master.

Files	Patch %	Lines
crates/curp/src/server/sp_wal/mod.rs	78.92%	13 Missing and 34 partials :warning:
crates/curp/src/server/sp_wal/segment.rs	88.73%	11 Missing and 14 partials :warning:
crates/curp/src/server/sp_wal/codec.rs	88.57%	15 Missing and 9 partials :warning:
crates/curp/src/server/sp_wal/error.rs	0.00%	8 Missing :warning:
crates/curp/src/server/sp_wal/tests.rs	95.78%	6 Missing and 1 partial :warning:
crates/utils/src/wal/pipeline.rs	66.66%	3 Missing and 1 partial :warning:
crates/curp/src/server/sp_wal/config.rs	96.55%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #818 +/- ## ========================================== + Coverage 75.55% 75.99% +0.44% ========================================== Files 180 192 +12 Lines 26938 28334 +1396 Branches 26938 28334 +1396 ========================================== + Hits 20353 21533 +1180 - Misses 5366 5470 +104 - Partials 1219 1331 +112 ```

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