`WebUtility.UrlDecode` does not document conversion of '+' into ' '

The documentation for `UrlEncode` was updated in #3124 to indicate that ' ' is converted into '+' on encode.

However:
- [ ] The documentation for `UrlEncodeToBytes` needs the same update.
- [ ] The documentation for `UrlDecode` and `UrlDecodeToBytes` needs a similar update to indicate that '+' is converted into ' ' on decode.
- [ ] All of these pages give the example that `<` and `>` are encoded as `%3c` and `%3e`, but this is incorrect. `<` and `>` are encoded as `%3C` and `%3E`. RFC 3986 says "For consistency, URI producers and normalizers should use uppercase hexadecimal digits for all percent-encodings," and that's what the implementation does.