Read doc comments from call paths

Since #3971 we now have go-to definition support for call paths which is great. However, it seems that doc comments aren't displayed on hover requests for these tokens yet in the language server.

We should write tests against [this example](https://github.com/FuelLabs/sway/blob/master/sway-lsp/test/fixtures/tokens/paths/src/main.sw) to ensure doc comments are a handled for these tokens.

Start with the call-path example in sway-lsp/test/fixtures/tokens/paths/src/main.sw and inspect the language server's hover handling for those tokens. Add coverage showing that their doc comments appear in hover responses, then run the relevant language-server tests to verify the behavior.

Written by the indexing model from the issue text.