refactor: split manager into filter and spawner, rename worker to messenger

[mmta]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 90.74074% with 50 lines in your changes are missing coverage. Please review.

Project coverage is 95.47%. Comparing base (647382b) to head (634e860).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
- Coverage   95.82%   95.47%   -0.36%     
==========================================
  Files          32       33       +1     
  Lines        6158     5807     -351     
==========================================
- Hits         5901     5544     -357     
- Misses        257      263       +6     

Flag	Coverage Δ
unittests	95.47% <90.74%> (-0.36%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
server/src/backlog/manager/storage.rs	96.49% <ø> (ø)
server/src/backlog/mod.rs	97.19% <100.00%> (-0.01%)	⬇️
server/src/bin/dsiem-frontend.rs	82.84% <100.00%> (-0.42%)	⬇️
server/src/filter/cache.rs	88.23% <ø> (ø)
server/src/messenger.rs	94.52% <ø> (ø)
server/src/parser.rs	100.00% <100.00%> (ø)
server/src/rule.rs	99.44% <100.00%> (-0.12%)	⬇️
server/src/watchdog.rs	99.24% <ø> (-0.02%)	⬇️
server/src/bin/dsiem-backend.rs	89.11% <93.47%> (+0.99%)	⬆️
server/src/cmd_utils.rs	91.00% <61.53%> (-4.46%)	⬇️
... and 3 more

... and 17 files with indirect coverage changes