TLS UserAgent hook support for Lua

### Summary
The Lua module currently supports hooks for HTTP only, but doesn't support the [TLS UserAgent hooks ](https://docs.trafficserver.apache.org/en/latest/developer-guide/plugins/hooks-and-transactions/ssl-hooks.en.html#tls-hooks). I know nothing about C and very little about ATS's plugin model, so I have no idea what it would take to implement this, or if it's even possible with ATS's model. I thought I'd ask the question here to get some clarification as to whether this is possible, and if it is, whether it's a bad idea to do so.

### Background
I have a use case that is similar to the functionality provided by the [Certifier](https://docs.trafficserver.apache.org/en/latest/admin-guide/plugins/certifier.en.html) plugin, but with some extra requirements that would require significant changes in that module. These changes are very specific to my use case, adding some extra dependencies, and thus the changes would have a near-zero chance of being contributed back into the source. This leaves us with a permanent branch to maintain, which is bad for us.

If we had support for these hooks in the Lua module, I can do everything I want in Lua scripts, plus the work could be contributed back to the source so that everyone can benefit. If we're going to invest in developing a plugin, I believe that the Lua one is the right choice, but I wanted to confirm with people who know better as to whether this is the right path.