Rendering Methods portions of #24024

[jbrockmendel]

Uses Substitution for the strftime docstring instead of pinning it below the method.

Changes section titles from "Formatting" to "Rendering Methods" to match other classes.

This is a pre-requisite to another push I'm making to split less-trivial pieces off of #24024, figured it was a decent small-scope to get out of the way.

[pep8speaks]

Hello @jbrockmendel! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/arrays/datetimelike.py !

• There are no PEP8 issues in the file pandas/core/arrays/datetimes.py !

• There are no PEP8 issues in the file pandas/core/arrays/period.py !

• There are no PEP8 issues in the file pandas/core/arrays/timedeltas.py !

[codecov]

Codecov Report

Merging #24392 into master will decrease coverage by 0.01%.
The diff coverage is 58.82%.

@@            Coverage Diff             @@
##           master   #24392      +/-   ##
==========================================
- Coverage    92.3%   92.29%   -0.02%     
==========================================
  Files         162      162              
  Lines       51875    51884       +9     
==========================================
+ Hits        47883    47885       +2     
- Misses       3992     3999       +7

Flag	Coverage Δ
#multiple	90.7% <58.82%> (-0.02%)	⬇️
#single	42.99% <47.05%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
pandas/core/arrays/period.py	98.49% <100%> (-0.01%)	⬇️
pandas/core/arrays/datetimes.py	97.73% <25%> (-0.52%)	⬇️
pandas/core/arrays/timedeltas.py	86.63% <40%> (-0.53%)	⬇️
pandas/core/arrays/datetimelike.py	96.31% <85.71%> (-0.21%)	⬇️

---

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[codecov]

Codecov Report

Merging #24392 into master will decrease coverage by 0.01%.
The diff coverage is 58.82%.

@@            Coverage Diff             @@
##           master   #24392      +/-   ##
==========================================
- Coverage    92.3%   92.29%   -0.02%     
==========================================
  Files         162      162              
  Lines       51875    51884       +9     
==========================================
+ Hits        47883    47885       +2     
- Misses       3992     3999       +7

Flag	Coverage Δ
#multiple	90.7% <58.82%> (-0.02%)	⬇️
#single	42.99% <47.05%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
pandas/core/arrays/period.py	98.49% <100%> (-0.01%)	⬇️
pandas/core/arrays/datetimes.py	97.73% <25%> (-0.52%)	⬇️
pandas/core/arrays/timedeltas.py	86.63% <40%> (-0.53%)	⬇️
pandas/core/arrays/datetimelike.py	96.31% <85.71%> (-0.21%)	⬇️

---

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 8c58817...b355220. Read the comment docs.

[jreback]

thanks @jbrockmendel