Add AsyncioRunnable

[cwharris]

Moves the CoroutineRunnable from Morpheus' Sherlock feature branch to MRC and renames it to AsyncioRunnable as it is heavily dependent on asyncio. Adjustments were made such that the Scheduler would no longer own a task container and/or tasks, leaving the scheduler interface simpler. Instead, the runnable is responsible for the lifetime of the tasks it creates. This leaves the scheduler with a single responsibility.

Much of the code could be moved to MRC proper from PyMRC, but it's not immediately obvious where the code should live or whether it would be reused, so keeping it colocated with the AsyncioRunnable makes the most sense for now, imo.

[codecov]

Codecov Report

Merging #411 (f2369db) into branch-23.11 (1ebd4e2) will increase coverage by 0.28%.
The diff coverage is 95.04%.

Additional details and impacted files

@@               Coverage Diff                @@
##           branch-23.11     #411      +/-   ##
================================================
+ Coverage         73.45%   73.73%   +0.28%     
================================================
  Files               392      395       +3     
  Lines             13862    14132     +270     
  Branches           1050     1078      +28     
================================================
+ Hits              10182    10420     +238     
- Misses             3680     3712      +32     

Flag	Coverage Δ
cpp	70.24% <95.04%> (+0.93%)	⬆️
py	42.61% <25.00%> (+0.01%)	⬆️

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

Files	Coverage Δ
cpp/mrc/include/mrc/coroutines/scheduler.hpp	100.00% <ø> (+100.00%)	⬆️
...pp/mrc/src/public/exceptions/exception_catcher.cpp	100.00% <100.00%> (ø)
python/mrc/_pymrc/include/pymrc/coro.hpp	94.11% <100.00%> (+6.81%)	⬆️
...hon/mrc/_pymrc/include/pymrc/asyncio_scheduler.hpp	88.23% <88.23%> (ø)
...thon/mrc/_pymrc/include/pymrc/asyncio_runnable.hpp	95.31% <95.31%> (ø)

... and 14 files with indirect coverage changes

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[cwharris]

/merge