Fix #10135: Cost of building multiple objects might not match test

[2TallTyler]

Motivation / Problem

As reported in #10135 (thanks @James103 for the excellent diagnosis!), objects might not consent to being built based on the locations of other objects built within the same command — for example distance restrictions between wind turbines in OpenGFX+ Landscape.

This creates an assertion because the test command and the exec command don't match costs.

Description

Add the CMD_NO_TEST flag to CmdBuildObjectArea to tell OpenTTD we're okay with this potential difference in cost.

Closes #10135.

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 save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_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