autoconf: use include directives instead of recursing down cmd

No installation diff, dist lost
  -zfs-2.1.99/cmd/fsck_zfs/fsck.zfs
which was distributed erroneously, since it's generated

Also clean gitrev on clean

Also add -e 'any possible bashisms' to default checkbashisms flags,
and fully parallelise it and shellcheck, and it works out-of-tree, too

Also align the Release in the dist META file correctly

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13316

tests/zfs-tests/.gitignore

@@ -0,0 +1 @@
+bin

tests/zfs-tests/include/Makefile.am

@@ -1,3 +1,5 @@
+CLEANFILES =
+EXTRA_DIST =
 include $(top_srcdir)/config/Substfiles.am
 
 pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/include

tests/zfs-tests/tests/functional/pyzfs/Makefile.am

@@ -1,3 +1,5 @@
+CLEANFILES =
+EXTRA_DIST =
 include $(top_srcdir)/config/Substfiles.am
 
 pkgpyzfsdir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/pyzfs