Implement epoch based gc worker

[danielealbano]

This PR implements an epoch-based garbage collector worker built upon the epoch-based garbage collector component.

The logic is pretty simple:

• sets up the worker
• every X ms tries to collect the staged objects
• once it's marked for termination waits for all the threads associated with the epoch gc to terminate
• once they terminate performs a forced collection moving forward the epoch of each thread and running a collection
• once the collections are completed, it unregisters and frees the epoch_gc_threads

This approach replicates the fuzzy testing in the epoch_gc as it was built, on purpose, in the same way to test the workflow end to end.

[codecov[bot]]

Codecov Report

Base: 82.27% // Head: 82.46% // Increases project coverage by +0.19% :tada:

Coverage data is based on head (9a476fc) compared to base (6b39e37). Patch coverage: 94.12% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #260 +/- ## ========================================== + Coverage 82.27% 82.46% +0.19% ========================================== Files 156 157 +1 Lines 9656 9758 +102 ========================================== + Hits 7944 8046 +102 Misses 1712 1712 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `82.46% <94.12%> (+0.19%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/danielealbano/cachegrand/pull/260?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano) | Coverage Δ | | |---|---|---| | [src/epoch\_gc\_worker.c](https://codecov.io/gh/danielealbano/cachegrand/pull/260/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano#diff-c3JjL2Vwb2NoX2djX3dvcmtlci5j) | `94.12% <94.12%> (ø)` | | | [src/xalloc.c](https://codecov.io/gh/danielealbano/cachegrand/pull/260/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano#diff-c3JjL3hhbGxvYy5j) | `97.14% <0.00%> (+1.43%)` | :arrow_up: | | [src/epoch\_gc.c](https://codecov.io/gh/danielealbano/cachegrand/pull/260/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano#diff-c3JjL2Vwb2NoX2djLmM=) | `98.97% <0.00%> (+2.56%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Daniele+Salvatore+Albano)

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