Convert semantic token types to TextMate scopes

[sungshik]

Consider:

lexical Digit = @category="number" [0-9];

• Before this PR, the generated TextMate rule for Digit would just get scope name number. However, while number is a semantic token type, it is not one of the standard TextMate scope names in VS Code (VS Code reports "No theme selector" and doesn't highlight). For semantic highlighting, VS Code does the conversion from incoming semantic token types to TextMate scope names itself, but scope names in TextMate grammars are uninterpreted. Thus, we need to make sure that the Rascal-Textmate converter already converts semantic token types (that occur in a Rascal grammar) to standard TextMate scopes before inserting them in a TextMate grammar.
• After this PR, the generated TextMate rule gets scope name constant.numeric

Additionally, this PR also moves the conversion of legacy semantic token types into the general converter (used to be done only for Rascal's own grammar, but it should always be done). Tests were updated too.

[DavyLandman]

Smart to do this for all grammars out there 👍🏼.

Also, note that the usethesource/rascal#1928 issue exists that should at some point in the future normalize these categories. (and in turn cause extra mapping code to the lookup tables in this PR)