THUMB: Complete `PushPopReg`

[codecov-commenter]

Codecov Report

Base: 55.31% // Head: 55.64% // Increases project coverage by +0.32% :tada:

Coverage data is based on head (23a66bc) compared to base (dd4972a). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #149 +/- ## ========================================== + Coverage 55.31% 55.64% +0.32% ========================================== Files 32 32 Lines 1909 1923 +14 ========================================== + Hits 1056 1070 +14 Misses 853 853 ``` | [Impacted Files](https://codecov.io/gh/RIP-Comm/clementine/pull/149?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [emu/src/cpu/flags.rs](https://codecov.io/gh/RIP-Comm/clementine/pull/149/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-ZW11L3NyYy9jcHUvZmxhZ3MucnM=) | `100.00% <ø> (ø)` | | | [emu/src/cpu/arm7tdmi.rs](https://codecov.io/gh/RIP-Comm/clementine/pull/149/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-ZW11L3NyYy9jcHUvYXJtN3RkbWkucnM=) | `77.75% <100.00%> (+0.72%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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