Extend the test_prep/<test> and test_prep/all build targets, generated
from add_test(BUILD_DEPENDS) when CMAKE_TEST_BUILD_DEPENDS is enabled, to
the Makefile generators. Previously only the Ninja and FASTBuild
generators provided them.
Resolve each test's dependencies in a shared layer so all command-line
generators consume one result. cmTestGenerator now filters target
dependencies to build-system targets and records, for each file
dependency, the single target that produces it as a primary
custom-command output (cmGlobalGenerator::FindOutputOwningTarget). The
Makefile generators emit phony rules in CMakeFiles/Makefile2 depending on
<target>.dir/all, with top-level forwarding rules. Sharing the
resolution also stops Ninja and FASTBuild from emitting a dead test_prep
edge for a non-buildable (e.g. INTERFACE) BUILD_DEPENDS target.
On the Makefile generators a file dependency that no single target
produces, and a test whose name contains ':', cannot be expressed as a
recursive-make rule and are reported with a warning and skipped.
Fixes: #27879
