feat(experimental): Issue errors for unreachable match branches

[jfecher]

Description

Problem*

Resolves

Summary*

Implements "unreachable case" errors for patterns in match expressions that are redundant with other patterns.

Additional Context

This took more time than expected. While the initial error was easy it was surprisingly difficult to get it to stop erroring if there were also any other errors in constructing the match rows. E.g. a program like

match Some(3) {
    Some(x) => (),
    3 => (),
    None => (),
    None => (),
}

Will give a type error on 3 => (), but will also give a separate error saying that it is unreachable. This extra error broke existing match tests (which mostly only expect 1 error) and was difficult to remove since it is technically correct. In the end I opted to not compile the decision tree of a match at all if there were any errors in constructing the pattern rows. This is what Ante does and it seems to match Rust as well. Neither of those languages issue errors for obviously redundant cases like the second None => (), if there was a type error or a name resolution error in constructing the match tree.

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.