fix(ssa refactor): function inlining orphans calls

[joss-aztec]

Description

Problem*

After inlining the following program:

use dep::std;

fn main(cond: bool) {
    let res = inner1(cond);
    std::println(res);
}

fn inner1(cond: bool) -> Field {
    inner2(cond)
}

fn inner2(cond: bool) -> Field {
    if cond { 1 } else { 2 }
}

it would incorrectly reduce to:

fn main f3 {
  b0(v0: u1):
    call println(v3)
    return 
}

This was happening because at the close of the call to inner1, the block mapping was inappropriately used for identifying the location of the "return terminator", thus the function builder was switching to b0, instead of continuing from the end of the last inlined function.

Summary*

Annotate the inlined location analogous to a "return terminator" by using the the current_block instead of a stale mapping.

Documentation

• This PR requires documentation updates when merged.

  • I will submit a noir-lang/docs PR.
  • I will request for and support Dev Rel's help in documenting this PR.

Additional Context

PR Checklist*

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

[joss-aztec]

This PR in conjunction with #1749 fixes the test named 8_integration.

[jfecher]

Looks good, and good test.

I think we should change some wordings in the documentation though. Since blocks is not a 1 to 1 mapping as you mention lets remove mentions of this and update the docs accordingly.