Mark (BUILD_|LOCAL_)COPY_HEADERS as [more] deprecated

We've considered these deprecated for a while, and have reduced where
they may be used, but let's actually throw warnings and call them out
specifically now.

Bug: 130719878
Test: lunch aosp_arm; m nothing   [see no warnings]
Test: lunch aosp_crosshatch; m nothing   [see LOCAL_COPY_HEADERS warnings]
Test: lunch aosp_taimen; m nothing  [see BUILD_COPY_HEADERS warnings]
Change-Id: I8c12012366d84667de0d223bbde38d8b90419e36