Use new memory allocator 'jemallocator'

[jpraynaud]

Content

This PR includes the activation of a different memory allocator jemallocator through a feature. This will likely avoid having memory fragmentation resulting in resident memory of signer/aggregator not being correctly released when signing/proving Cardano transactions.

See https://github.com/input-output-hk/mithril/issues/1629#issuecomment-2069016167 for details.

Pre-submit checklist

• Branch
  • [x] Crates versions are updated (if relevant)
  • [x] CHANGELOG file is updated (if relevant)
  • [x] Commit sequence broadly makes sense
  • [x] Key commits have useful messages
• PR
  • [x] No clippy warnings in the CI
  • [x] Self-reviewed the diff
  • [x] Useful pull request description
  • [x] Reviewer requested

Issue(s)

Closes #1629

[github-actions[bot]]

Test Results

    3 files  ±0     43 suites  ±0   8m 25s :stopwatch: +17s   928 tests ±0    928 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  1 022 runs  ±0  1 022 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit e4715961. ± Comparison against base commit 188d8b78.

:recycle: This comment has been updated with latest results.