ewaol-tests: Update directory structure and variables to support multiple suites

This patch moves files for a specific runtime integration test suite into a
separate corresponding folder, leaving only common files in a shared folder.
Common recipe code is also moved to an .inc file that can be shared between
multiple integration test suite recipes.

Environment variables that would be used by multiple integration test suites
are made generic (e.g. TEST_LOG_FILE), but are initialised by the prefixed
version for the corresponding suite (e.g. CE_TEST_LOG_FILE).

This patch also adds in-source clarification that test log messages with a
message type of FAIL will implicitly produce an additional DEBUG message that
contains the ${status} and ${output} variables (these are normally defined by
BATS) as well as the latest contents of ${TEST_STDERR_FILE}.

Issue-Id: SCM-2366
Signed-off-by: Richard Neill <richard.neill@arm.com>
Change-Id: Iff27838b9fb835fc4cd0e6c26b255f1f6cef5312