Make show/hide link in RC individually localizable

This commit concerns the filters on the [[Special:RecentChanges]] box.
Previously, "Show" and "Hide" in messages such as "Show anonymous users" were a
shared system message: now each filter can be assigned a verb individually.

For example:
* Argument $1 of `rcshowhideminor` used to come from `show` or `hide`.
* $1 now comes from `rcshowhideminor-show` or `rcshowhideminor-hide`.

In place of `show` and `hide`, the following system messages are affected:
* `rcshowhideminor` uses `rcshowhideminor-show` and `rcshowhideminor-hide`.
* `rcshowhidebots` uses `rcshowhidebots-show` and `rcshowhidebots-hide`.
* `rcshowhideanons` uses `rcshowhideanons-show` and `rcshowhideanons-hide`.
* `rcshowhidepatr` uses `rcshowhidepatr-show` and `rcshowhideanons-hide`.
* `rcshowhidemine` uses `rcshowhidemine-show` and `rcshowhidemine-hide`.

This change attempts to correct an issue encountered when localising into
Chechen (ce); previous behaviour made it impossible to translate the entire
sentence fragment correctly (as the verb is rendered slightly differently
depending on the rest of the sentence, and this was not possible with a shared
Show/Hide message).

Bug: 58449
Change-Id: Ibbfc3cd0477b029c8f22a3c812a891ac2109d660
Merge "Make show/hide link in RC individually localizable"