Update build examples with meson wrap files

[jeromekelleher]

Once we have #1960 we can update the build examples for meson. (See #1958 also) We should update:

• https://github.com/tskit-dev/tskit/tree/main/c/tests/meson-subproject
• Developer documentation
• https://github.com/tskit-dev/tskit-build-examples/

Note that the changes in #1958 changed the directory structure also, so these will need to be tweaked. It may be better to avoid git submodules entirely in the examples repo, and just use the shipped tarballs instead. We can download manully in the Makefile and use the wraps for meson.

One thing that's not clear is whether we can automatically pull in kastore using the tskit dependency, or whether this has to be at the top level also. It would be nice if we could just specify the tskit dep and let things work themselves out from there.

[jeromekelleher]

Now that we're vendoring in kastore (#1973) we should be able to simplify this quite a bit

[benjeffery]

I'm going to do this right after 1.0 so it can use the 1.0 tarball.