Refactor ci flow

[yanganto]

• CI will use MSRV from Rust manifest (Cargo.toml)
• Reduce usage of actions-rs, which are no longer maintained after Oct 13, 2023.
• Set up dependency upgrade bot
• Refactor lint, test, build with Nix
• Allow codecov upload failure

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.7%. Comparing base (c014bad) to head (c8c7246).
Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master     #89     +/-   ##
========================================
- Coverage    47.7%   47.7%   -0.0%     
========================================
  Files          34      34             
  Lines        3149    3154      +5     
========================================
+ Hits         1503    1504      +1     
- Misses       1646    1650      +4     

Flag	Coverage Δ
rust	47.7% <ø> (-<0.1%)	⬇️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[dr-orlovsky]

ACK c8c7246