feat(ios): Add optional delegate to retrieve player in native side

[Minishlink]

Useful when you want to access the player in native side (eg. for SharePlay/GroupActivities)

Related issue #2444

In AppDelegate.m:

#import "RCTVideoPlayerViewController.h"

...

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    MyVideoPlayerDelegate *myVideoPlayerDelegate = [[MyVideoPlayerDelegate alloc] init];
    RCTVideoPlayerViewController.videoPlayerDelegate = myVideoPlayerDelegate;

In MyVideoPlayerDelegate.swift (works also in equivalent objective-c...)

import AVFoundation

@objc(MyVideoPlayerDelegate)
class MyVideoPlayerDelegate : NSObject, RCTVideoPlayerDelegate {
  func playerDidAppear(_ player: AVPlayer!) {
    // do something when player is mounted
  }

  func playerDidDisappear() {
    // do something when player is unmounted
  }
}

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. If you are having a similar problem, please open a new issue and reference this one instead of commenting on a stale or closed issue.

[hueniverse]

Closing due to lack of response (from the original submitted or anyone else to review and rebase). If someone wants to pick this up please open a new PR that ports this code into the current master. We are doing our best to start clean with v6 which requires being a bit aggressive in closing stale PRs that are over a year old. Please don't consider this dismissing of your work and contribution - it's greatly appreciated.

[Minishlink]

@hueniverse Is there something missing in this PR? Is v6 completely in Swift now?

[hueniverse]

Yes, we switched to Swift. It was closed because there has been no activity on it after the stale bot warning 2 months ago. I don't know if there is anything wrong with the PR other than no one else showed interest in the feature or reviewing it.