Remove `netbsdpe` support

netbsdpe was deprecated in c2ce8313.
Since then, a release has passed (2.37), and it was marked obselete in
5c9cbf07. Unless I am mistaken, that
means we can now remove support altogether.

All branches in the "active" code are remove, and the target is
additionally marked as obsolete next to the other removed ones for
libbfd and gdb.

Per [1] from the NetBSD toolchain list, PE/COFF support was removed a
decade ago. Furthermore, the sole mention of this target in the binutils
commit history was in 2002. Together, I'm led to believe this target
hasn't seen much attention in quite a while.

[1]: https://mail-index.netbsd.org/tech-toolchain/2021/06/16/msg003996.html

bfd/
	* config.bfd: Remove netbsdpe entry.
binutils/
	* configure.ac: Remove netbsdpe entry.
	* testsuite/lib/binutils-common.exp (is_pecoff_format): Likewise.
	* configure: Regenerate.
gas/
	* configure.tgt: Remove netbsdpe entry.
gdb/
	* configure.tgt: Add netbsdpe to removed targets.
ld/
	* configure.tgt: Remove netbsdpe entry.
	* testsuite/ld-bootstrap/bootstrap.exp: Likewise.