fix: incorrect worker state when worker reach IdleTTL

[rustatian]

Reason for This PR

closes: roadrunner-server/roadrunner#1669

Description of Changes

• Create additional worker states for max_memory/ttl/idlettl.
• Set TTL reached state only if the worker is in ready state. Otherwise, if the worker is currently handling a request, set the invalid state so that the worker watcher (not supervisor) will reallocate such a worker when it returns a response to the user.
• Handle SoftJob state correctly.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under
the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.]
[Reviewer TODO: Verify that these criteria are met. Request changes if not]

• All commits in this PR are signed (git commit -s).
• The reason for this PR is clearly provided (issue no. or explanation).
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.

[codecov]

Codecov Report

Merging #84 (0f9bb09) into stable (d72a218) will decrease coverage by 0.79%.
The diff coverage is 72.34%.

@@            Coverage Diff             @@
##           stable      #84      +/-   ##
==========================================
- Coverage   83.09%   82.31%   -0.79%     
==========================================
  Files          22       22              
  Lines        1922     1922              
==========================================
- Hits         1597     1582      -15     
- Misses        270      283      +13     
- Partials       55       57       +2     

Files Changed	Coverage Δ
events/events.go	66.66% <0.00%> (-4.77%)	⬇️
fsm/fsm.go	68.75% <14.28%> (-7.49%)	⬇️
worker/worker.go	83.38% <70.58%> (-1.35%)	⬇️
pool/static_pool/supervisor.go	93.57% <100.00%> (-2.13%)	⬇️
worker_watcher/worker_watcher.go	89.04% <100.00%> (ø)

... and 2 files with indirect coverage changes