Ensure correct sleep in 'rmw_wait' (backport #344)

[mergify]

Description

Because of truncation and rounding issues, there are some edge cases where rmw_wait() can sleep for less time than the indicated.

Main changes

• Round non-zero ended nanosecond times up to the next millisecond
• Since uxr_millis() rounds the clock time down (e.g. 100.9 ms to 100 ms), one more loop iteration is often needed when now == deadline

  ---

  This is an automatic backport of pull request Ensure correct sleep in 'rmw_wait' #344 done by Mergify.

[mergify]

This pull request does not currently match the merge queue conditions, so it cannot be queued from here. The box comes back if it matches again.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.85%. Comparing base (efbd887) to head (d569c25).
⚠️ Report is 1 commits behind head on kilted.

Additional details and impacted files

@@            Coverage Diff             @@
##           kilted     #345      +/-   ##
==========================================
- Coverage   55.63%   54.85%   -0.78%     
==========================================
  Files         102      101       -1     
  Lines        6072     5897     -175     
  Branches     1011      929      -82     
==========================================
- Hits         3378     3235     -143     
+ Misses       2345     2327      -18     
+ Partials      349      335      -14     

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