User-Agent should include receiver type

[mwbrooks]

Description

We should start to include the receiver type (HttpReceiver, SocketModeReceiver, AwsLambdaReceiver, ExpressReceiver) in the user-agent string. This would allow us to understand the adoption of each receiver and prioritize missing features based on usage.

What type of issue is this? (place an x in one of the [ ])

• [ ] bug
• [x] enhancement (feature request)
• [ ] question
• [ ] documentation related
• [ ] example code related
• [ ] testing related
• [ ] discussion

Requirements (place an x in each of the [ ])

• [x] I've read and understood the Contributing guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.
• [x] I've searched for any related issues and avoided creating a duplicate issue.