Click-type-test

- Add a parameter, `overrides`, to `check_param_annotations` which can be used
to skip type deduction and use a hard-coded value instead

- The type annotation used as the return type of a `callback` on a parameter
will now be treated as an override which takes precedence over any deduction
about the parameter type
- The type annotation used as the return type of a custom type's `convert`
method will be checked and used as the annotated value for parameter types
which do not implement `AnnotatedParamType`
- The documentation is more explicit about type evaluation logic and order of
overrides

- Fix handling for required options, non-required arguments, `nargs=-1`, and
`nargs=N` for `N>1`

- Enhance documentation and examples
- Add support for `click.Path(path_type=...)` as a type or a callable with an
annotated return type. Unsupported `path_type` values will raise `TypeError`.
- A new parameter is supported for `check_param_annotations`,
`known_type_names`, a mapping of type values to strings.
`check_param_annotations` will use this mapping in a best-effort fashion to
display the names of types in `BadAnnotation` errors.

- Remove `ExplicitlyAnnotatedOption` from the library due to issues with
usability. It is now kept in the `examples/` directory
- Rename `AnnotatedOption` to `AnnotatedParameter` to encompass `Argument`
subclasses as well

- Fix release process to include build artifacts in github releases