tests: refactor test_api* to support the D-Bus API and add a new test

Implemented a `TargetApi` enum to make the process of implementing
tests for the D-Bus and HTTP API more convenient.

Refactored `test_api_{create_boot, shutdown, pause_resume, delete}` tests
with the `TargetApi` enum to also implement tests for the D-Bus API.

Added a new test named `test_api_dbus_and_http_interleaved` that uses
both the HTTP and D-Bus API at the same time.

Modified integration test scripts to enable the `dbus_api` feature when
compiling and start a dbus-session when integration tests are run.

Signed-off-by: Omer Faruk Bayram <omer.faruk@sartura.hr>

scripts/dev_cli.sh

@@ -426,7 +426,7 @@ cmd_tests() {
             --env USER="root" \
             --env CH_LIBC="${libc}" \
             "$CTR_IMAGE" \
-            ./scripts/run_integration_tests_"$(uname -m)".sh "$@" || fix_dir_perms $? || exit $?
+            dbus-run-session ./scripts/run_integration_tests_"$(uname -m)".sh "$@" || fix_dir_perms $? || exit $?
     fi
 
     if [ "$integration_sgx" = true ]; then