Adding step_time and iteration to CycleMapContext

[unlessgames]

Implementing #81 as discussed, while also adding the iteration counter to the map context as it's useful there as well.

I've included a helper to make the code a bit more streamlined around setting stuff on lua callbacks across the codebase while handling the error. This can be reverted of course if the more verbose way is preferred.

Note, src/gate/scripted.rs called reset on the callback twice, I assume that was a copy-paste typo.

[github-actions]

Benchmark for 5d79cc6

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	50.9±0.82µs	51.6±0.43µs	+1.38%
Cycle/Parse	310.0±4.17µs	319.2±4.27µs	+2.97%
Rust Phrase/Clone	421.4±4.61ns	448.1±5.11ns	+6.34%
Rust Phrase/Create	64.9±0.89µs	66.9±0.74µs	+3.08%
Rust Phrase/Run	607.9±5.71µs	621.7±4.92µs	+2.27%
Rust Phrase/Seek	131.7±242.41µs	134.2±248.33µs	+1.90%
Scripted Phrase/Clone	642.0±16.74ns	647.0±6.23ns	+0.78%
Scripted Phrase/Create	1007.8±28.33µs	1001.6±22.49µs	-0.62%
Scripted Phrase/Run	1653.1±11.62µs	1626.0±18.48µs	-1.64%
Scripted Phrase/Seek	217.8±440.94µs	205.4±410.94µs	-5.69%

[emuell]

Looks good. Thanks. The handle thing is nice as well to get rid of all this error boilerplate.