1.44.0 release, version bump

[YifeiZhuang]

No description provided.

[dapengzhang0]

In the 1st commit, we should make the following change:

• README.md: gRPC-Java works with JDK 7 -> gRPC-Java works with JDK 8
• build.gradle: protobufVersion = '3.19.1' -> protobufVersion = '3.19.2'
• protoc version 3.19.1 to 3.19.2
  L115 <protocArtifact>com.google.protobuf:protoc:3.19.1:exe:${os.detected.classifier}</protocArtifact>
  L143 artifact = "com.google.protobuf:protoc:3.19.1"

[dapengzhang0]

@YifeiZhuang Can you rebase, by moving and squashing the last commit with the first commit?

git rebase -i HEAD~4

pick 1st commit
s 4th commit
pick 2nd commit
pick 3rd commit

And then force push to the PR?