fix: Fix if/match tracking in last uses pass

[jfecher]

Description

Problem*

Resolves #8923

Summary*

The BranchesPath in some situations could get confused as being the same as a prior if. E.g. in

if true {
    if true {
        foo(b);
    }
}

if true {
    if false {
    } else {
        foo(b);
    }
}

We tried to move b both times previously because we tracked Branch0 { Branch0 { use } } and left it intact until the next use which looks compatible, so they were merged into Branch0 { Branch0 { use }, Branch1 { use } }. To fix this I tagged each if and match with its own unique id.

Additional Context

This is a draft currently because I need to add a test

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

Changes to number of Brillig opcodes executed

Generated at commit: f95cfb2b753ddc32a40d07d813c2f9a9e0d23c08, compared to commit: d1e55d93e31cefc8331d8f1174f56db87a995374

🧾 Summary (10% most significant diffs)

Program	Brillig opcodes (+/-)	%
slices_inliner_max	-3 ✅	-0.12%

---

Full diff report 👇

Program	Brillig opcodes (+/-)	%
slices_inliner_max	2,490 (-3)	-0.12%

[github-actions]

Changes to Brillig bytecode sizes

Generated at commit: f95cfb2b753ddc32a40d07d813c2f9a9e0d23c08, compared to commit: d1e55d93e31cefc8331d8f1174f56db87a995374

🧾 Summary (10% most significant diffs)

Program	Brillig opcodes (+/-)	%
slice_regex_inliner_zero	-12 ✅	-0.74%
slice_regex_inliner_max	-24 ✅	-1.19%

---

Full diff report 👇

Program	Brillig opcodes (+/-)	%
slices_inliner_min	2,160 (-3)	-0.14%
slices_inliner_zero	1,622 (-3)	-0.18%
regression_1144_1169_2399_6609_inliner_min	992 (-3)	-0.30%
slices_inliner_max	1,684 (-9)	-0.53%
slice_regex_inliner_min	1,849 (-12)	-0.64%
slice_regex_inliner_zero	1,620 (-12)	-0.74%
slice_regex_inliner_max	1,992 (-24)	-1.19%

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 6cc264a	Previous: b04a51c	Ratio
rollup-merge	0.004 s	0.003 s	1.33

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[asterite]

Looks great! And it seems the code ends up being simpler too.