Add moq-gst-ietf

[englishm]

Like #14, but includes the full history (via git-subtree) and then renames the crate to avoid confusion.

If we run into issues with the big gstreamer dependency tree this brings in, I may move it back out into a separate repo again, but I'm OK trying this for now.

[englishm]

Looks like we'll needs something like this, which is kind of gross to do for everything when it's really only necessary for moq-gst-ietf:

moq-rs/moq-gst-ietf/.github/workflows/pr.yml

Lines 22 to 24 in d57f08a

	# We need gstreamer installed to compile this repo
	- name: Setup GStreamer
	uses: blinemedical/setup-gstreamer@v1

(Incidentally, there's a bit more cleanup I see I can do here of things pulled in by the subtree merge)

[englishm]

Hmm, yeah.. Issues like this where our build can break because of build issues with dependencies of dependencies.. don't make me super excited about pulling this in to the main repo.

  Run-time dependency pangocairo found: NO (tried pkgconfig and cmake)
  Looking for a fallback subproject for the dependency pangocairo
  Downloading pango source from https://download.gnome.org/sources/pango/1.50/pango-1.50.12.tar.xz
  A fallback URL could be specified using source_fallback_url key in the wrap file
  
  subprojects/gst-plugins-base/ext/pango/meson.build:11:12: ERROR: Incorrect hash for source:
   caef96d27bbe792a6be92727c73468d832b13da57c8071ef79b9df69ee058fe3 expected
   85180957e333f90ec8e8d84c3110041c0637d789c9b28a606f7f2965eb7ddc8c actual.

While this type of thing could theoretically happen with any of our deps, pulling in all of GStreamer as a requirement for cargo build greatly increases our exposure to this type of risk. It also places this burden on contributors (who may have more diverse development environments) and I'd rather not add extra complications there if we can avoid it.

I think it does make sense to keep a version of moq-gst in sync with the IETF MoQ WG drafts, but it might be better to continue that in a separate repo. I can port these changes over to https://github.com/englishm/moq-gst (and probably rename the repo to moq-gst-ietf to match) if that's helpful.

Thoughts, @levaitamas?

[levaitamas]

hi @englishm !
Thanks for taking the initiative on this. The separate repo makes sense to me, and I am happy to help maintain it. I will send a PR to make it work with the IETF version.