Consolidate suboptimal usages of which() under one linter

[IndrajeetPatil]

To lint for instances of which(x == min(x)) or which(x == max(x)), which should be avoided in favour of more efficient which.min() or which.max(), respectively.

Ref: https://csgillespie.github.io/efficientR/performance.html

[MichaelChirico]

Great observation!

I would rather name it which_optimum_linter(), or combine it with the pending which_grepl_linter() from #884 and just call it which_linter() more generally

[IndrajeetPatil]

Sounds like a plan! Thanks.

I guess I will wait for WhichGreplLinter to be ported over to {lintr} and then build on top of it to consolidate all of it into which_linter().

[MichaelChirico]

One issue I have here is which(grepl(.)) could either go under a which_linter() umbrella or a regex_linter() umbrella.

It's not clear to me how to prefer one or the other.

[IndrajeetPatil]

As astutely noted by @AshesITR, the two versions of the code in the original post aren't equivalent and therefore don't make a good candidate for a new linter. Pity.

#2684 (comment)