lib: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

Normalize the g(eom,cache,part,...) build.

Rather then combining hardlink creation for the geom(8) binary with
shared library build, move libraries to src/lib/geom so they are
built and installed normally. Create a common Makefile.classes
which is included by both lib/geom/Makefile and sbin/geom/Makefile
so the symlink and libraries stay in sync.

The relocation of libraries allows libraries to be build for 32-bit
compat. This also reduces the number of non-standard builds in
the system.

This commit is not sufficent to run a 32-bit /sbin/geom on a 64-bit
system out of the box as it will look in the wrong place for libraries
unless GEOM_LIBRARY_PATH is set appropriatly in the environment.

Reviewed by: bdrewery
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D15360