cmake: move global headers to specific checks

cmake: move global headers to specific checks

Before this patch we added standard headers unconditionally to the
global list of headers used for feature checks. This is unnecessary
and also doesn't help CMake 'Generate' performance. This patch moves
these headers to each feature check where they are actually needed.
Stop using `stddef.h`, as it seems unnecessary.

I've used autotools' `m4/curl-functions.m4` to figure out these
dependencies.

Also delete checking for the C89 standard header `time.h`, that I
missed in the earlier commit.

Ref: 96c29900bcec32dd6bc8e9857c8871ff4b8b8ed9 #11940

Closes #11951