Build: Export test configs in dedicated files

Split regression test specific config flags and PSA Arch tests specific
config flags from common TF-M configs exported from secure build.

NS build will include a clean sep_config.cmake without test specific
configs, in actual NS integration.

Signed-off-by: David Hu <david.hu@arm.com>
Change-Id: I89650b7f8a124018aa61e67f1e61d48aa15745be
4 files changed