feat(location): expose iOS activityType and automatic-pause signal

[sedwo]

Core Location has two iOS behaviours the plugin never surfaced, both of which matter to apps recording continuous tracks.

CLLocationManager.activityType was left at Core Location's .other default, so an app had no way to describe the kind of movement it is recording. Apple documents the property as a hint for how fixes are acquired and processed: it informs when updates may be paused automatically, and for automotiveNavigation that reported positions may be adjusted towards nearby roads. Adds Location.setActivityType() and the LocationActivityType enum. The call returns the activity type actually in effect afterwards, read back from the native manager, so callers can confirm what was applied instead of assuming it (#602).

locationManagerDidPauseLocationUpdates(_:) was not implemented, so a pause Core Location decided on by itself was only ever visible as an absence of updates, which is indistinguishable from a location stream that has broken. Adds Location.onLocationUpdatesPaused, emitting true on pause and false on resume.

Both are iOS-only: setActivityType returns null and onLocationUpdatesPaused stays empty on Android, macOS and web, which have no equivalent setting. The platform interface gives both members benign default implementations rather than throwing UnimplementedError, so third-party platform implementations keep compiling untouched.

LocationActivityType crosses the method channel by index, so its declaration order mirrors CLActivityType's raw values and is pinned by a test.

Bumps location to 10.1.0 and location_platform_interface to 7.1.0, with CHANGELOG, README and docs updates, unit tests for both packages, and regenerated mockito mocks.

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