[Parser] Parse rethrow

[tlively]

Like delegate, rethrow takes a Try label. Refactor the delegate handling so
that Try can share its logic.

[tlively]

Current dependencies on/for this PR:

• main
  • PR [Parser] Parse table operations #6154
    • PR [Parser] Parse rethrow #6155 👈
      • PR [Parser] Parse the remaining array operations #6158
        • PR [Parser] Parse string types and operations #6161

This stack of pull requests is managed by Graphite.

[aheejin]

Nice that this can be simpler after you did all the hard work in #6128! Can we add a test where rethrow is in the try part of the innermost try (and catch part of an outer try) as well?