Make minor performance improvements using ruff rules C4 and PERF

[cclauss]

Issue number of the reported bug or feature request: #

Describe your changes
A clear and concise description of the changes you have made.
Make minor performance improvements using ruff rules C4 and PERF.

9	PERF102	[*] When using only the keys of a dict use the `keys()` method
9	PERF401	[ ] Use a list comprehension to create a transformed list
4	C401   	[*] Unnecessary generator (rewrite as a `set` comprehension)
4	C402   	[*] Unnecessary generator (rewrite as a `dict` comprehension)
4	C408   	[*] Unnecessary `dict` call (rewrite as a literal)
3	C405   	[*] Unnecessary `list` literal (rewrite as a `set` literal)
1	C416   	[*] Unnecessary `dict` comprehension (rewrite using `dict()`)

Testing performed
Describe the testing you have performed to ensure that the bug has been addressed, or that the new feature works as planned.
% ruff --select=C4,PERF .

Additional context
Add any other context about your contribution here.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c4b35f3) 92.32% compared to head (b556a9a) 92.22%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #500      +/-   ##
==========================================
- Coverage   92.32%   92.22%   -0.10%     
==========================================
  Files          91       91              
  Lines       11033    11033              
  Branches     1524     1524              
==========================================
- Hits        10186    10175      -11     
- Misses        842      853      +11     
  Partials        5        5              

Flag	Coverage Δ
cpp	85.66% <ø> (-0.31%)	⬇️
python_and_cython	95.48% <100.00%> (ø)

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[godlygeek]

Everything under benchmarks/ is vendored code that we don't want to modify - please revert the changes to those files. We should instead configure ruff to not lint that directory. Also, we should configure ruff to always apply the C4 and PERF rules if we're going to make these changes, since otherwise there's nothing stopping us from regressing on them.

All the changes to our source code and tests seem fine, though. I think some of the dictionary literals are a bit less readable than the calls to the dict() constructor they're replacing, but the difference is probably not enough to worry about.

[godlygeek]

LGTM! Thanks for the contribution, @cclauss!