[iOS/macOS] Add option to automatically build (and sign / archive) bundles.

[bruvzg]

• Adds generate_bundle build flag to automatically generate .app bundle or template zip.
• Adds bundle_sign_identity to automatically sign editor .app bundle with correct entitlements (defaults to ad-hoc signing is not set).

scons platform=macos target=editor arch=x86_64
scons platform=macos target=editor arch=arm64 generate_bundle=yes
# generates and signs editor app bundle with universal executable.

scons platform=macos target=template_release arch=x86_64
scons platform=macos target=template_release arch=arm64
scons platform=macos target=template_debug arch=x86_64
scons platform=macos target=template_debug arch=arm64 generate_bundle=yes
# generates ZIP with the full macOS export template (debug and release universal executable).

scons platform=ios target=template_release arch=arm64
scons platform=ios target=template_release arch=x86_64 ios_simulator=yes
scons platform=ios target=template_release arch=arm64 ios_simulator=yes
scons platform=ios target=template_debug arch=arm64
scons platform=ios target=template_debug arch=x86_64 ios_simulator=yes
scons platform=ios target=template_debug arch=arm64 ios_simulator=yes generate_bundle=yes
# generates ZIP with the full iOS export template (debug and release universal xcframeworks for device and simulator).

Fixes godotengine/godot-proposals#1460

[akien-mga]

Looks good to me overall.

[akien-mga]

Thanks!