runtime/syntax: Highlight built-in constants in Python

[f4nb0y]

Optionally highlight https://docs.python.org/3/library/constants.html as Constant

Ref: #17788
Attn: @dkearns @zvezdan

[dkearns]

Thanks @f4nb0y.

I think it would be more flexible to always match the booleans and other constants without the config variable guard as pythonBoolean, and pythonConstant, in the initial keyword block around line 100, and hi-link them by default to pythonStatement, Statement, or Keyword. This is how pythonAsync is handled, for example.

The config variable would then only override the hi-link commands.