Fix locale generation on debian base distros

[paulober]

Proposed Commit Message

fix(debian): Fix locale generation

The current debian apply_locale implementation
depends on a modified locale-gen script that
only exists on ubuntu systems. This patch
fixes the generation of new locales
and should also work on ubuntu
with out the reliance on the custom
locale-gen patch.

Fixes GH-6471

Additional Context

#6471

Test Steps

Try setting a locale on debian 13 with the current cloud-init release. It will run without problems but not generate the selected locale because locale-gen doesn't support locale-gen <locale> but want you select the locales in /etc/locale.gen prior to the execution of this script.

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

@tdewey-rpi