ci: select Xcode by version through DEVELOPER_DIR (#3545)

[datlechin]

Why

The xcode-27 image names Apple's released Xcode 27A9275 Xcode_27.1_Release_Candidate.app. On release/0.82, setup-xcode with require-release rejects that folder name, so the v0.82.0 tag's app job would fail.

Change

• Cherry-pick of ci: select Xcode by version through DEVELOPER_DIR #3545: setup-xcode takes Xcode by its bundle's version, exports DEVELOPER_DIR, and require-release checks the build and licenseType instead of the folder name.
• Conflict in ios-tests.yml: the line has no ci(ios): boot the simulator while the app builds #3547 boot step, so only sudo comes off its xcodebuild -downloadPlatform iOS.

Verified

setup-xcode/action.yml equals main's. actionlint, check-test-plans.py and verify.sh agent-docs pass.

Not in this PR

• The line's tree now differs from v0.82.0-beta.1 outside the changelog, so v0.82.0 needs a beta.2 first.