[Docs] Assorted parameter doc updates

- Adds a new section on "infer-only" parameters using the `//` sigil.
- Adds a new section on parameter inference including struct parameter
inference.
- Adds a new section clarifying the difference between the terms
"generic" and "parameterized."

MODULAR_ORIG_COMMIT_REV_ID: 3455f903637af7cce450ff980ec1a520bf04565d