refactor(makefile): consolidate the make targets used for bats tests (#1746)

New examples of running tests:

1. To run a specific bats file (with and without verbose output):
make run-blackbox-tests BATS_TEST_FILE_PATH=test/blackbox/delete_images.bats
make run-blackbox-tests BATS_TEST_FILE_PATH=test/blackbox/delete_images.bats BATS_VERBOSITY=2

2. To run the CI tests (with and without verbose output)
make run-blackbox-ci
make run-blackbox-ci BATS_VERBOSITY=2

BATS_TEST_FILE_PATH is used to pass on the test file to run using `run-blackbox-tests`
BATS_VERBOSITY controls the verbosity of the bats framework output, if unspecified the output only
contains test results and failure message in case of failures.
If BATS_VERBOSITY is 1, then also show commands as they are executed.
If BATS_VERBOSITY is 2, on top of the above it also shows output of passed tests.

Other changes in this PR:
- Update some of the tests to show logs after the run ends.
- Run the linters before the tests, as it saves time on failures when running in GH

Signed-off-by: Andrei Aaron <aaaron@luxoft.com>

test/blackbox/pushpull_authn.bats

@@ -69,7 +69,8 @@ function setup_file() {
     }
   },
   "log":{
-    "level":"debug"
+    "level":"debug",
+    "output": "${BATS_FILE_TMPDIR}/zot.log"
   }
 }
 EOF
@@ -77,6 +78,11 @@ EOF
     wait_zot_reachable 8080
 }
 
+function teardown() {
+    # conditionally printing on failure is possible from teardown but not from from teardown_file
+    cat ${BATS_FILE_TMPDIR}/zot.log
+}
+
 function teardown_file() {
     zot_stop_all
 }