Optimize if-matches case

[johnynek]

the pattern:

if x matches p:
  trueCase
else:
  falseCase

was being compiled into:

b = match x:
  case p: True
  case _: False

match b:
  case True: trueCase
  case False: falseCase

rather than relying on optimization later, it's easy to detect this pattern while still at the source AST and directly convert to:

match x:
  case p: trueCase
  case _: falseCase

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.66%. Comparing base (04a0e87) to head (479e241). Report is 23 commits behind head on main.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1193 +/- ## ========================================== + Coverage 91.32% 91.66% +0.34% ========================================== Files 96 96 Lines 11846 12070 +224 Branches 2675 2744 +69 ========================================== + Hits 10818 11064 +246 + Misses 1028 1006 -22 ```

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