fix(experimental): Fix execution of match expressions with multiple branches

[jfecher]

Description

Problem*

Resolves #7323

Summary*

Our SSA flattening pass still doesn't support > 2 predecessors on a block so lower a match by jumping to a new block each time instead. Each end block is merged LIFO like nested if statements. This is less efficient than jumping to the end directly or merging the blocks tournament-bracket style but flattening supports neither of those options.

Additional Context

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]

⚠️ Performance Alert ⚠️

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

Benchmark suite	Current: 32934cb	Previous: 899e8c8	Ratio
rollup-block-root-single-tx	123 s	101 s	1.22

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

CC: @TomAFrench

[vezenovm]

The circuit size report failure is strange. I could call bb info locally with that new test.

[vezenovm]

The circuit size report failure is strange. I could call bb info locally with that new test.

The error actually looks to not have to do with bb. It was failing on the rebuild.sh script which simply executes the circuit. We fail with the following:

I didn't expect this as I thought the nargo_cli tests would fail but I see we are already gating for the enums feature in those tests.

I simply excluded this test from the rebuild script.