[improvement]: Support libsrtp3

[Ra2-IFV]

Improvement Description

I was having a hard time building asterisk with libsrtp until I realized I'm using lastest commit of libsrtp and it builds libsrtp3.* now

[jcolp]

Are you working on this?

[Ra2-IFV]

I'm just simple user, I can only help modifying .ac files and testing. I don't know if they did some breaking changes, I can't help.
btw libsrtp3 is not released, it's only on main branch