fix(ssa refactor): Change the result of simplifying Eq and Lt to bool

[jfecher]

Description

Problem*

This was a small issue I saw while testing main_bool_arg where when an Eq or Lt are simplified from known constants, the result was the operand type rather than bool. This later prevented optimizing the not instruction afterward.

Summary*

This PR sets out to

Example

Before:

After:

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]

LGTM