put standard library file associations in package.json

[bobbrow]

Fixes: #4077

This change disables C_Cpp.autoAddFilesAssociations by default and lists the standard headers in package.json to associate them with C++. Other extensionless headers will not get special treatment, but their languageId will still be fixed when a goto definition command is handled.

[sean-mcmanus]

Can you add the missing extensionless system headers?

ccomplex
cfenv
cinttypes
contracts
cstdalign
cstdbool
cstdint
ctgmath
cuchar
debugging
hazard_pointer
hive
inplace_vector
linalg
rcu
simd
text_encoding

[sean-mcmanus]

Is this for 1.28.3? Or 1.29.0? Seems like 1.29.0 might be better...I was worried about something breaking regarding the language handling.

[sean-mcmanus]

Does this change potentially break something contributed by VS Code itself and/or should the change be made in VS Code itself?

[sean-mcmanus]

What about the other "languages" fields like "aliases" and "configuration" -- should those be set? Does VS Code set those and/or do we inherit those if we don't set the fields?

[bobbrow]

Can you add the missing extensionless system headers?

Yes. It looks like I did not include headers removed since their introduction and new C++26 headers.

[sean-mcmanus]

VS Code uses

        "aliases": [
          "C++",
          "Cpp",
          "cpp"
        ],
        "configuration": "./language-configuration.json"

Do you know how to check if that is still inherited?

[sean-mcmanus]

Should we add the GSL library extensionless files? VS has those added (maybe others?).

[sean-mcmanus]

Should we generate/update this list of filenames by reading a shared file with VS which also has a similar list of extension less files? We could do that similar to the import-edge-strings script.

Or otherwise, should it manually match VS?