Automatic annotation of top-level type signatures

[smores56]

We want to let users have Roc give their functions an inferred type signature. There are a few ways we want to provide this:

Our LSP should provide two new code actions:

1. "Add signature" to this value, either at top level or within a function/block
2. At the top of the file, "Add signatures to all top-level defs" with missing signatures

We also want our formatter to have a new subcommand annotate that will add signatures to all top-level defs in a file with missing signatures. e.g. roc format annotate <file.roc>