MM-14559 Rewrite existing plugin API tests to exclusively test via actual plugin (#10494)

* initial work on rewriting test cases using the raw literal format

* split out the embedded tests into separate file and implement the test using a generic tester function

* initial work on rewriting test cases using the raw literal format

* split out the embedded tests into separate file and implement the test using a generic tester function

* moved tests to separate dir to avoid conflicts

* removed duplicate files

* added license header

* fixed plugin paths

* moved all trivial tests to separate files
created "meta-test" that scans a folder of api tests and runs them

* remove rpc tests from make

* use fileutil.FindDir instead of pwd
clean up the test files

Makefile

@@ -70,7 +70,7 @@ TESTFLAGS ?= -short
 TESTFLAGSEE ?= -short
 
 # Packages lists
-TE_PACKAGES=$(shell go list ./...)
+TE_PACKAGES=$(shell go list ./...|grep -v plugin_tests)
 
 # Plugins Packages
 PLUGIN_PACKAGES=mattermost-plugin-zoom mattermost-plugin-jira