Simplify pull request checklist

[trexfeathers]

Description

• Simplifies the pull request checklist
• Moves the pull request checklist directly into the pull request template (see below) - to make it more immediate and therefore easier to follow
• Updates several related pages with more detailed guidance on contributing

Checklist

(In addition to a full set of passing checks ✅)

• Included a What's New entry
• Incorporated type hints in any changed code
• Checked if tests need updating
• Checked if benchmarks need updating
• Checked if documentation needs updating
  • Docstrings (we love code examples!)
  • User Manual pages
• Checked if dependencies need updating

---

Tip

Add any of the below labels to trigger actions on this PR:

• benchmark_this Request that this pull request be benchmarked to check if it introduces performance shifts

[scitools-ci]

Templating

This PR includes changes that may be worth sharing via templating. For each file listed below, please either:

• Action the suggestion via a pull request editing/adding the relevant file in the SciTools/.github templates/ directory. ¹
• Raise an issue against the SciTools/.github repo for the above action if you really don't have 10mins spare right now. Include an assignee, to avoid it being forgotten.
• Dismiss the suggestion if the changes are not suitable for templating.

You will need to dismiss this review before this PR can be merged. Recommend the reviewer does this as their final action before merging, as this text will continually update as commits come in.

Templated files

The following changed files are templated:

• benchmarks/README.md, templated by SciTools/.github/templates/benchmarks/README.md
• benchmarks/custom_bms/README.md, templated by SciTools/.github/templates/benchmarks/custom_bms/README.md
• benchmarks/custom_bms/install.py, templated by SciTools/.github/templates/benchmarks/custom_bms/install.py
• benchmarks/custom_bms/tracemallocbench.py, templated by SciTools/.github/templates/benchmarks/custom_bms/tracemallocbench.py

Footnotes

1. Include this text in the PR body to avoid any notifications about applying the template changes back to the source repo!
   @scitools-templating: please no update notification on: iris ↩

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.15%. Comparing base (76cf13e) to head (01fbd2c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7096   +/-   ##
=======================================
  Coverage   90.15%   90.15%           
=======================================
  Files          91       91           
  Lines       24977    24977           
  Branches     4684     4684           
=======================================
  Hits        22518    22518           
  Misses       1682     1682           
  Partials      777      777           

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[trexfeathers]

...
This PR includes changes that may be worth sharing via templating. For each file listed below, please either:
...

See SciTools/.github#264

[ESadek-MO]

Honestly looks great, I can't see anything controversial, which is always unsettling on documentation 😂

A couple questions, and your original suggestion to add a lifeline to the checklist for newer users, and I think it'd be good to go.

[ESadek-MO]

Thanks @trexfeathers, lets get this in.

Minor and irrelevant