dyno: Fix bugs that were breaking chpl-language-server tests

[dlongnecke-cray]

This PR fixes bugs that were causing test failures in chpl-language-server.

Make sure to skip resolving function bodies in resolveFunction if the function does not have one (e.g., for extern functions).

If typedSignatureInitial is called on a nested function and parent frames are not present, emit a warning and continue if the parent(s) are generic instead of returning nullptr. Future work should make typedSignatureInitial take the parent function signature instead.

Reviewed by @mppf. Thanks!

TESTING

• linux64, standard
• test-chpl-language-server

[dlongnecke-cray]

@mppf Daniel pointed out some logic bugs that I should fix first before I ping you for review.