[FR] Add HTTP2 support for sendEach() and sendEachForMulticast()

[honorhs]

When will HTTP/2 support be available for methods like sendEach() and sendEachForMulticast() in the Firebase Admin Java SDK?

It appears that this support has already been implemented in firebase-admin-node.
https://github.com/firebase/firebase-admin-node/releases/tag/v12.3.0

I was informed that after implementing HTTP/2 in firebase-admin-node, the same would be applied to firebase-admin-java.
#834 (comment)

Thank you.

[honorhs]

@lahirumaramba @jonathanedey

[jhkim-grip]

#974 show that api deprecation is started but where is the http2 support?

[ratuka]

It would have been nice to release a new version before the deprecation.

[lahirumaramba]

This will be addressed in #979

[lahirumaramba]

Fixed in #1013

[jonathanedey]

HTTP/2 support has now been added with the release of v9.4.0.
See our wiki for more information on this change.