we reduce boiler-plate by having a common set of log fields that are defined once.
infologger.level constant is used instead of "level".
"cmd" and "command" log fields were unified to "command".

Launch is broken into smaller pieces for better readability.
Some minor error handling bugs are automatically fixed on the occasion and some more are marked with fixme and will be taken care of in separate commits.

it's difficult to trigger such an error, but if taskCmd.Start() actually fails, it never sets taskCmd.Process, so trying to use the PID there is a nil access and causes executor to crash.

If a task fails to report STANDBY state upon startup, we now perform the standard TERM, INT, KILL sequence instead of just KILL.
We also rely on Wait() to close relevant pipes and provide us with exit code.
All above is moved into a dedicated method which will be reused in next fixes.

Fixes OCTRL-1075

Bumps [github.com/expr-lang/expr](https://github.com/expr-lang/expr) from 1.17.0 to 1.17.7.
- [Release notes](https://github.com/expr-lang/expr/releases)
- [Commits](expr-lang/expr@v1.17.0...v1.17.7)

---
updated-dependencies:
- dependency-name: github.com/expr-lang/expr
  dependency-version: 1.17.7
  dependency-type: direct:production
...

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