Clean up doc comments and add periods

[connortsui20]

Problem

Cleans up a bit of the CPS PR.

Summary of changes

This commit adds periods to all of the comments in the cir and engine. I also added some more detail here and there.

This commit also unifies all of the types in the cir to make it easier to interact with those types. Imo it makes more sense to have them all in one place rather than to have to figure out the paths to each of them every time you import.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.30864% with 20 lines in your changes missing coverage. Please review.

Project coverage is 73.3%. Comparing base (60c275f) to head (0f36b12).

Files with missing lines	Patch %	Lines
optd-core/src/bridge/into_cir.rs	0.0%	11 Missing ⚠️
optd-core/src/bridge/from_cir.rs	0.0%	3 Missing ⚠️
optd-core/src/cir/expressions.rs	0.0%	2 Missing ⚠️
optd-core/src/cir/plans.rs	0.0%	2 Missing ⚠️
optd-core/src/engine/eval/binary.rs	75.0%	2 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
optd-core/src/cir/rules.rs	0.0% <ø> (ø)
optd-core/src/engine/eval/core.rs	100.0% <100.0%> (ø)
optd-core/src/engine/eval/expr.rs	95.1% <100.0%> (ø)
optd-core/src/engine/eval/match.rs	99.0% <100.0%> (ø)
optd-core/src/engine/eval/mod.rs	96.6% <ø> (ø)
optd-core/src/engine/eval/operator.rs	100.0% <100.0%> (ø)
optd-core/src/engine/eval/unary.rs	80.8% <100.0%> (ø)
optd-core/src/engine/mod.rs	6.4% <100.0%> (ø)
optd-core/src/engine/test_utils.rs	100.0% <100.0%> (ø)
optd-core/src/engine/utils.rs	100.0% <ø> (ø)
... and 10 more

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[SarveshOO7]

I think I prefer the old comment here.

[SarveshOO7]

the eg. of what S and T can be is helpful

[connortsui20]

In general I dislike comments that explain the function signature essentially verbatim, they don't really add anything in helping someone understand why this function is here and ends up cluttering headspace.