Ensure all string enum values are comparable to strings

[jwortmann]

This is part of a workaround for a problem described at sublimelsp/LSP#2446 (comment)

Currently it would not work on Python 3.8 to import directly from enum, because most of the enums with string values are just regular Enum instead of StrEnum. This means we can't compare values to the strings from a server response. But if they are StrEnum, they could be compared directly (in theory, because StrEnum is not part of Python 3.8 - but this means that the enums inherit from our fake StrEnum class, instead of to the real Enum class from the enum module).

I think then it should work, together with another small change I have in mind.

[predragnikolic]

In the last commit LanguageKind enum type was also added.

Note, LanguageKind requires additional code changes in the LSP codebase.

6bb8d43#diff-5b016df699e02c42aafd75508568d98c635c0a233622d3f3ff79a92b0e7ddff3L3347-R3464

-    languageId: str
+    languageId: 'LanguageKind'

[jwortmann]

Thanks, and good that you noticed that.

I think we cannot yet update the protocol.py file in LSP, because in the last PR I added this new value
https://github.com/sublimelsp/LSP/blob/5891ff41deaa781783effeb97c978b3e50bd0a26/plugin/core/protocol.py#L219-L220

but it is not yet added upstream in the https://github.com/microsoft/lsprotocol repo. Or alternatively if we want to update, we need to add it back manually.

Forget that, I see now that it is already in the upstream repo. I must have had something else in mind.