tests: 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/

Enable SO_LINGER to the so_reuseport_lb_test regression tests, preventing
many sockets in TIME_WAIT state at the end of the test.

PR: 249885
Reviewed by: markj
Approved by: markj
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D26549

Revert r361237, it's fixed by r361231

PR: 246560
Sponsored by: The FreeBSD Foundation

Temporarily disable test case causes kernel panic in CI:

- sys.netinet.so_reuseport_lb_test.basic_ipv6

PR: 246560
Sponsored by: The FreeBSD Foundation

so_reuseport_lb_test: correct setsockopt parameter size

Change type of variable used in setsocketopt so correct size of
option is passed.

Test failure was identified when running the test on PowerPC64,
and the following error message was seen:

"bind () failed: Address already in use"

Submitted by: Fernando Valle <fernando.valle@eldorado.org.br>
Reviewed by: melifaro, adalava
Approved by: jhibbits (mentor)
Sponsored by: Eldorado Research Institute (eldorado.org.br)
Differential Revision: https://reviews.freebsd.org/D24164

Rename the SO_REUSEPORT_LB test file to be consistent with other tests.

MFC after: 1 week