Codechange: Add and use Rect WithX/WithY methods.

[PeterN]

Motivation / Problem

Often we have a Rect but need to set the left and right, or top and button, coordinates directly. This requires decomposing the Rect into a new one, making sure that parameters are the correct signed type.

Sometimes they are set based on another existing Rect.

Description

Add WithX() and WithY() SetX() and SetY() methods to Rect, in two forms: one takes two coordinates to replace left and right or top and bottom as appropriate, the other takes another Rect, and does the same.

Update some places that deconstruct Rect to use WithX() or WithY() SetX() or SetY(). Unlikely to be exhaustive.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker

[LordAro]

(warning, bike shedding) how about WithX ? Set implies it modifies the original object

[PeterN]

(warning, bike shedding) how about WithX ? Set implies it modifies the original object

Good call, that's why (some of) the current methods are With...

I did also consider SetLeftRight, so maybe SetX -> WithLeftRight, but also maybe WithX is fine.