stage2: Include `catch` expressions in error return trace

[topolarity]

Follow-up to #12837. Wanted to separate this one out since it's a change to UX.

The idea is to make it easier to track errors that flow through a catch block:

fn foo() !void { return error.BigIssue; }
fn bar() !void { return error.AnotherProblem; }
fn baz() !void {
    return bar();
}
test {
    foo() catch {
        try baz();
    };
}

./test_err9.zig:1:18: 0x2117c8 in foo (test)
fn foo() !void { return error.BigIssue; }
                 ^
./test_err9.zig:7:11: 0x211918 in test_0 (test)
    foo() catch {
          ^
./test_err9.zig:2:18: 0x2118e8 in bar (test)
fn bar() !void { return error.AnotherProblem; }
                 ^
./test_err9.zig:4:5: 0x2118ce in baz (test)
    return bar();
    ^
./test_err9.zig:8:9: 0x211934 in test_0 (test)
        try baz();
        ^

This trace makes it clear that an error arrived in test_0 and then was handled unsuccessfully.

Any if (foo()) |non_err| { ... } else |err| { ... } expressions are also included in the return trace.

Dependent on #12837 , only the last commit is specific to this PR.