[VSCE][Feature] Function/parameter descriptions shown on hover

### Is this your first time submitting a feature request?

- [x] I have read the [expectations for open source contributors](https://docs.getdbt.com/docs/contributing/oss-expectations)
- [x] I have searched the existing issues, and I could not find an existing issue for this feature
- [x] I am requesting a straightforward extension of existing dbt functionality, rather than a Big Idea better suited to a discussion

### Which version of dbt is this feature for?

dbt v2.x (Core or Fusion)

### Describe the feature

When typing or autocompleting a function, the completion list shows a description of the function and its parameters. That same description is not available when hovering over the function elsewhere in the file.

### Describe alternatives you've considered

Hovering over a function call should surface the same description and parameter info shown in the autocomplete list so a user can quickly confirm the behavior.

### Who will this benefit?

_No response_

### Are you interested in contributing this feature?

_No response_

### Anything else?

_No response_