Refactor #find_versions parameters in strategies

[samford]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

Livecheck's strategies all contain a #find_versions method that takes input (e.g., a url, regex, cask, etc.) and uses it to identify versions from a source. All of the strategies except for ExtractPlist expect that a URL will be provided. ExtractPlist is an exception (in many unfortunate ways), as it expects a cask instead of a URL.

When ExtractPlist was created, a cask parameter was added to every #find_version method. This is because livecheck uses all the possible arguments when it calls the method, regardless of the strategy (i.e., it doesn't cater the arguments to what the strategy expects). If a strategy didn't have the cask parameter but a named cask argument was provided, Ruby would give an error.

Ideally, a given #find_versions method should only be required to have parameters for what it actually uses and we shouldn't have to update every method if one strategy needs a new parameter. This PR aims to achieve this by removing unused parameters from #find_versions methods and including an **unused parameter in each, as the double splat will take care of any arguments that don't correspond to a named parameter for a given strategy.

For example, ExtractPlist has a named cask: parameter (since it's the only strategy that works with a cask) but all the others omit this. Instead of producing an error, the cask parameter is simply part of unused (i.e., unused[:cask]).

In general, this helps to minimize #find_versions parameters to only what's used. This will make it easier to add new strategies in the future, where a new parameter wouldn't need to be added to all other strategies. Besides that, this bit of clean up helps to make things a bit more manageable before I add a couple more parameters to most #find_versions methods in the near future.

---

As usual, I've done comparative before/after livecheck runs across first-party formulae/casks and I didn't see any regressions.

[BrewTestBot]

Review period will end on 2021-08-13 at 22:30:10 UTC.

[BrewTestBot]

Review period ended.

[maxim-belkin]

Proposed changes seem reasonable to me: this PR transforms some of the required arguments to keyword arguments and hides the cask keyword argument inside the unused hash, where appropriate. I have one question (see the apache.rb), but overall 👍🏻 from me.