fix: cast-aware reconfigure to preserve Chromecast session

[Jmilham21]

Summary

• When Chromecast is active and a config change is triggered from React Native, recreatePlayerWithConfig was calling configurePlayer which reinitializes the player and tears down the SDK's internal CastProvider, killing the cast session.
• Now uses loadPlaylist instead of configurePlayer when actively casting, preserving the cast session while loading new content.
• Fixes podspec flag accumulation bug where USE_GOOGLE_CAST was silently dropped when both Cast and IMA were enabled.
• Fixes setUpCastController crash (playerView.player as! Bool) and adds support for playerViewController.
• Properly tracks isCasting state in cast delegate callbacks.

Blocked on native SDK change

This PR is awaiting a native iOS SDK (JWPlayerKit) update to expose a public method for parsing Delivery API JSON into JWPlayerItem objects. Once available, the RN wrapper can use it to properly parse playlist items during casting, ensuring DRM sources/credentials are correctly forwarded to the cast receiver.

Non-DRM casting works as expected with the current changes.

Test plan

• Verify non-DRM content can be cast and config changes (e.g. loading new playlist) preserve the cast session
• Verify the cast session is not torn down on config changes while casting
• Verify full player recreation (license/viewOnly change) gracefully handles active cast sessions
• Verify both Cast and IMA flags compile correctly together (podspec fix)
• Pending: DRM content casting after native SDK update