Change return type of get_time_set_period and get_time_set_edge to datetime.timedelta

[sbethur]

• This contribution adheres to CONTRIBUTING.md.

• I've updated CHANGELOG.md if applicable.

• I've added tests applicable for this pull request

What does this Pull Request accomplish?

Change return type of get_time_set_period and get_time_set_edge to datetime.timedelta.

List issues fixed by this Pull Request below, if any.

Partial fix for Issue 1397

What testing has been done?

Tests have been updated as required. CI will run the tests.

[codecov]

Codecov Report

Merging #1437 into master will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1437      +/-   ##
==========================================
- Coverage   91.92%   91.85%   -0.08%     
==========================================
  Files          20       22       +2     
  Lines        3655     4433     +778     
==========================================
+ Hits         3360     4072     +712     
- Misses        295      361      +66     

Flag	Coverage Δ
#codegenunittests	88.24% <ø> (ø)
#nidigitalsystemtests	91.51% <ø> (?)
#nifakeunittests	96.40% <ø> (ø)
#nimodinstunittests	95.37% <ø> (ø)
#nitclkunittests	95.45% <ø> (ø)

Impacted Files	Coverage Δ
...digital/nidigital/history_ram_cycle_information.py	100.00% <0.00%> (ø)
generated/nidigital/nidigital/_library.py	91.12% <0.00%> (ø)

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[marcoskirsch]

#1397 says hightime.TimeDelta. This PR uses datetime.TimeDelta.
This shouldn't close #1397 just yet, right?

[sbethur]

#1397 says hightime.TimeDelta. This PR uses datetime.TimeDelta.
This shouldn't close #1397 just yet, right?

That's right, I updated the PR description to prevent auto-linking to 1397.