chore: Show the step number in the SSA message

[aakoshh]

Description

Problem*

Resolves having to scroll up and down the SSA trying to find a particular pass.

Summary*

Adds the overall step number to the SSA "After" message, so we can refer to a step by absolute position and look up a step in the pipeline a bit easier when we're looking at console output.

❯ cargo run -q -p nargo_cli -- compile --silence-warnings --force --show-ssa-pass Simple --show-ssa-pass Defunct
After Initial SSA:
brillig(inline) fn main f0 {
...
After Dead Instruction Elimination (3) (step 43):
brillig(inline) predicate_pure fn main f0 {
  b0():
    return
}

In the above example (3) (step 43) means this is the 3rd occurrence of the DIE pass, and overall this is the 43rd SSA pass.

Additional Context

The output from cargo test -p noir_ast_fuzzer_fuzz pass_vs_prev and #8647 include a step number along with the message. If we want to look up the state of the SSA before/after this step in an overall output we get from --show-ssa, we either have to know where the pass is, or use string search in a text editor to find it. By including the step count in the output of --show-ssa, it should be easier to find the step in a large console output by scrolling down and looking for the number, because we always see where we are relative to what we are looking for.

Implementation notes

The reason we're not printing something like "step 4 of 43" is because the SsaBuilder doesn't necessarily know how many steps we are going to execute.

And the reason for deriving the count from the Map that contains how many times a specific message was encountered, rather than maintaining a separate counter, is so that we don't have to take another stateful variable to give to the SsaBuilder used to execute the secondary pipeline.

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.

[asterite]

Nice!