LU-16962 build: parallel header checks

LU-16962 build: parallel header checks

Add LB2_CHECK_LINUX_HEADER_SRC and LB2_CHECK_LINUX_HEADER_RESULT
macros to use for running header checks in parallel.

Migrate (most) header checks to parallel and run a subset
early as the results of those tests are required by other
configure tests.

Test-Parameters: trivial
HPE-bug-id: LUS-11710
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: Ia765261179d25e96912e65e31c81824b4507e604
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51673
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>