Add match guard let chain drop order and scoping tests
We have a bunch of tests for if let chain drop order, but those tests don't cover match guard chains to the same depth. This PR adds the following tests:
* match guard equivalents of the if let chains tests in the `drop-order-comparisons.rs` test, added by #133605.
* match guard equivalent of the `mir_let_chains_drop_order.rs` test, added by #107251
* match guard equivalent of `temporary-early-drop.rs`, added by #133093
The added tests all have variants for 2021 and 2024, showing that the behavior on both editions matches that of if let chains on 2024.
tracking issue: https://github.com/rust-lang/rust/issues/51114
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