sys: Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Create in-tree LINT files

Now that config(8) has supported include for 19 years, transition to
including the NOTES files. include support didn't exist at the time,
nor did the envvar stuff recently added. Now that it does, eliminate
the building of LINT files by just including everything you need.

Note: This may cause conflicts with updating in some cases.
find sys -name LINT\* -rm
is suggested across this commit to remove the generated LINT
files.

Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D26540