Remove autotools build

No dist check on the CI, since it doesn't really
add anything in the Meson case (tarball is based
on files checked into git and srcdir != builddir).
Tests are too flaky on the CI so dist will always
fail when running checks as part of the distcheck.

TODO:
 - ci: update submit-to-coverity
7 jobs for remove-autotools in 8 minutes and 53 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #1577518
build meson

00:00:26

passed #1577520
1809 windows docker
build msvc amd64

00:05:39

passed #1577521
1809 windows docker
build msvc x86

00:05:40

passed #1577519
1809 windows docker
build msys2

00:08:53

 
  Test
passed #1577524
doc-and-install meson

00:00:43

passed #1577522
test meson

00:01:11

passed #1577523
test valgrind meson

00:01:15