waveform: Implement copy and pickle

[bkeryan]

• This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

Enable support for the standard copy and pickle modules.

Add tests for copy.copy, copy.deepcopy, and pickle.

Remove copy usage from equality tests.

Document that waveform timing objects are immutable and change their constructor to copy the timestamps list by default.

Why should this Pull Request be merged?

Closes AB#3107357: Support copy/pickle

What testing has been done?

Ran updated tests.

[github-actions]

Test Results

   10 files  ±    0     10 suites  ±0   25s ⏱️ ±0s
  497 tests +  106    497 ✅ +  111  0 💤  -  5  0 ❌ ±0 
4 970 runs  +1 060  4 970 ✅ +1 110  0 💤  - 50  0 ❌ ±0 

Results for commit 985ba65. ± Comparison against base commit 375f6da.

This pull request removes 28 and adds 134 tests. Note that renamed tests count towards both.

tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value0]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value1]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value2]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value3]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value4]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value5]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value6]
tests.unit.waveform._timing.test_precision ‑ test___deep_copy___equality___equal[value7]
tests.unit.waveform._timing.test_precision ‑ test___different_value___equality___not_equal[lhs0-rhs0]
tests.unit.waveform._timing.test_precision ‑ test___different_value___equality___not_equal[lhs1-rhs1]
…

tests.unit.waveform._scaling.test_linear ‑ test___different_value___equality___not_equal[left0-right0]
tests.unit.waveform._scaling.test_linear ‑ test___different_value___equality___not_equal[left1-right1]
tests.unit.waveform._scaling.test_linear ‑ test___different_value___equality___not_equal[left2-right2]
tests.unit.waveform._scaling.test_linear ‑ test___different_value___equality___not_equal[left3-right3]
tests.unit.waveform._scaling.test_linear ‑ test___different_value___equality___not_equal[left4-right4]
tests.unit.waveform._scaling.test_linear ‑ test___different_value___equality___not_equal[left5-right5]
tests.unit.waveform._scaling.test_linear ‑ test___same_value___equality___equal[left0-right0]
tests.unit.waveform._scaling.test_linear ‑ test___same_value___equality___equal[left1-right1]
tests.unit.waveform._scaling.test_linear ‑ test___scale_mode___copy___makes_shallow_copy
tests.unit.waveform._scaling.test_linear ‑ test___scale_mode___deepcopy___makes_deep_copy
…

♻️ This comment has been updated with latest results.