ENH: Update settings

[Miksus]

This PR has several changes:

• No longer warns on missing task_execution. Now default is async
• Renamed config option task_execution to execution
• Renamed task argument permanent_task to permanent
• Exposed the task lock class. Now it should be possible to create a custom lock to run multiple Rocketry instances.

[codecov-commenter]

Codecov Report

Base: 94.88% // Head: 94.87% // Decreases project coverage by -0.00% :warning:

Coverage data is based on head (55156a2) compared to base (50d16db). Patch coverage: 94.28% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #152 +/- ## ========================================== - Coverage 94.88% 94.87% -0.01% ========================================== Files 80 80 Lines 4454 4466 +12 ========================================== + Hits 4226 4237 +11 - Misses 228 229 +1 ``` | [Impacted Files](https://codecov.io/gh/Miksus/rocketry/pull/152?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli) | Coverage Δ | | |---|---|---| | [rocketry/core/task.py](https://codecov.io/gh/Miksus/rocketry/pull/152/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli#diff-cm9ja2V0cnkvY29yZS90YXNrLnB5) | `91.18% <77.77%> (-0.23%)` | :arrow_down: | | [rocketry/application.py](https://codecov.io/gh/Miksus/rocketry/pull/152/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli#diff-cm9ja2V0cnkvYXBwbGljYXRpb24ucHk=) | `100.00% <100.00%> (ø)` | | | [rocketry/core/schedule.py](https://codecov.io/gh/Miksus/rocketry/pull/152/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli#diff-cm9ja2V0cnkvY29yZS9zY2hlZHVsZS5weQ==) | `93.50% <100.00%> (+0.36%)` | :arrow_up: | | [rocketry/session.py](https://codecov.io/gh/Miksus/rocketry/pull/152/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli#diff-cm9ja2V0cnkvc2Vzc2lvbi5weQ==) | `95.89% <100.00%> (+0.16%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mikael+Koli)

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