devel/llvm16: add a lite FLAVOR

The lite flavor is for when you just need a FreeBSD compiler (e.g., in
CI). By default it includes CLANG and LLD as well as backends required
for FreeBSD and FreeBSD ports (BE_NATIVE, BE_AMDGPU, and BE_WASM).

The lite install is ~350GiB on amd64 vs ~1.9GiB for default and it has
only a single dependency (zstandard). (The goal was no dependencies,
but libzstd is a private lib in base.)

Due to 16.0.1 support being merged without predecessors the resulting
packages have a version (16.0.1_1) that has not (yet) appeared in main.
Hopefully they will resync when 16.0.2 is released.

Sponsored by: DARPA
(cherry picked from commit 003b969feea21d4759a4c87815c843f0b6ebbf8f)