Add support for x86_64-only cores on Apple Silicon builds

[jamesxhart]

Add support for x86_64-only cores for Apple Silicon builds, and arm64-only cores for Apple Silicon Macs running builds with Rosetta. (#5016) (OpenEmu builds should support Universal, x86_64-only (for Intel Macs, or Apple Silicon Macs with Rosetta installed), and arm64-only (for Apple Silicon Macs) cores, regardless of the architecture being used by OpenEmu.)

Uses /usr/bin/arch to launch the appropriate slice of OpenEmuHelperApp for the core being used.

As per Apple - Porting to Apple Silicon, the XPC service for OpenEmuHelperApp has been split to x86_64-only and arm64-only, to support launching both core architectures simultaneously.

Launching an x86-64-only core from Apple Silicon (or an arm64-only core from OpenEmu running Rosetta) will override the "Run games using" setting in Settings > Secrets, and always launch using XPC.

Universal cores with unsigned arm64 code are launched with the x86_64 slice instead.

An option in Settings > Secrets shows the installed core architecture (under a "Kind" column in Settings > Cores).

If a core contains no valid architectures, an error is shown with the heading "The [core name] core could not be loaded", and message "The installed version of the [core name] core is not supported on this platform. Try updating to the latest version from the Cores preferences.".

For Intel Macs launching arm64-only cores, the message is "The [core name] core is not supported on this platform. An Apple Silicon Mac is required.".

(For Apple Silicon Macs launching x86_64-only cores after Rosetta is depreciated (beginning with macOS 28), the message is also "The installed version of the [core name] core is not supported on this platform. Try updating to the latest version from the Cores preferences.")

Added:

• option “Show core architecture” under a new group "Cores" in Settings > Secrets, to display the core architecture
• label under "Run games using" in Settings > Secrets, to show “Cores with different architectures to OpenEmu will always launch using XPC.”
• strings to localization (for English only)

(I wasn't able to test the build with an Intel Mac.)

Settings > Cores, with the debug option "Show core architecture" enabled:

Settings > Secrets, showing the label under "Run games using", and the Cores group with “Show core architecture”:

Error when loading a game, for Intel Macs launching arm64-only cores:

Error when loading a game, with the corresponding core (otherwise) containing no valid architectures: