Eliminate warnings on `sbt doc` and `sbt unidoc` (#1470)

* Eliminate warnings on `sbt doc` and `sbt unidoc`
- removed toFirrtl reference on MultiTargetAnnotation
- lots of places where package path has to be added to comment references
- Change to use `/** text starts here` convention when wrong in comment with a doc fix.
  - Did not exhaustively change these
- Wrestled doc example in RenderDiGraph#renderNode, not sure if I won
- Cleaned up InferWidths & CatchExceptions imports
- Added missing license message to a couple of files.
- fixed a couple of stale parameter names in scaladoc
- Added @unchecked to stop erasure warning in Emitting where emission annotations are collected
- Change types to [_] on match in RenameMap#recordAll to fix erasure warning

* Where  possible change [[firrtl.ir.X]] to [[firrtl.ir.X X]] for better display in scaladoc

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>