Add RenameTestCases transformer

[bhirsz]

I've decided to split #183 into test case and keyword names.

I've also removed unnecessary characters from class descriptions and added url to transformer detailed docs to each description.

Closes #190

[codecov-commenter]

Codecov Report

Merging #191 (ea83531) into main (53d1e69) will decrease coverage by 0.05%.
The diff coverage is 95.45%.

❗ Current head ea83531 differs from pull request most recent head 3c172de. Consider uploading reports for the commit 3c172de to get more accurate results

@@            Coverage Diff             @@
##             main     #191      +/-   ##
==========================================
- Coverage   97.37%   97.31%   -0.06%     
==========================================
  Files          25       26       +1     
  Lines        1409     1452      +43     
==========================================
+ Hits         1372     1413      +41     
- Misses         37       39       +2     

Impacted Files	Coverage Δ
robotidy/transformers/AlignSettingsSection.py	96.87% <ø> (ø)
robotidy/transformers/AlignVariablesSection.py	96.00% <ø> (ø)
robotidy/transformers/DiscardEmptySections.py	100.00% <ø> (ø)
robotidy/transformers/MergeAndOrderSections.py	100.00% <ø> (ø)
robotidy/transformers/NormalizeAssignments.py	100.00% <ø> (ø)
robotidy/transformers/NormalizeNewLines.py	98.80% <ø> (ø)
...obotidy/transformers/NormalizeSectionHeaderName.py	100.00% <ø> (ø)
robotidy/transformers/NormalizeSeparators.py	100.00% <ø> (ø)
robotidy/transformers/NormalizeSettingName.py	100.00% <ø> (ø)
robotidy/transformers/OrderSettings.py	100.00% <ø> (ø)
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 53d1e69...3c172de. Read the comment docs.