undesirable_function_linter() could support a custom regex?

[MichaelChirico]

I am looking at the default undesirable_function_linter() throwing for this:

par('usr')

because the default looks for any call to par(). But actually, what the lint reasoning really cares about is writing device settings, not reading them.

So we might want to tweak the XPath for par(): //SYMBOL_FUNCTION_CALL[text() = 'par']/parent::expr/following-sibling::EQ_SUB, i.e. it has to use a keyword argument.

I think this feature is quite generalizable -- I've definitely encountered situations where a function is undesirable in some-but-not-all circumstances, and rather than introducing a new par_linter() (or generally foo_linter()) every time there's a minor rule that's just outside of what undesirable_function_linter() can accomplish, it would be good to extend undesirable_function_linter() itself to be able to handle these situtations.

What remains is to come up with a good design for this. The first thing that comes to mind is to accept a list instead of just a string:

undesirable_function_linter(c(par = '...'))

undesirable_function_linter(list(par = list(lint_message = '...', xpath = '...')))

I think this would also help with (if not obviate) #1912, #1770.