Refactor push message for Hipchat service

What does this MR do?

It now uses the PushMessage that was originally for the Slack service. It has a presenter, because the links for Slack and Hipchat are different. This improves the flog score of HipchatService#create_push_message.

Are there points in the code the reviewer needs to double check?

I removed the ending whitespace for the messages in Hipchat. The new and removed branch/tag messages have an ending newline. I am not sure whether this is needed. The branch/tag update message did not have it.

Why was this MR needed?

For issue #3444 (closed), this improves the flog score.

What are the relevant issue numbers?

#3444 (closed)

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