[MM-62408] Server Code Coverage with Fully Parallel Tests (#30078)

* TestPool

* Store infra

* Store tests updates

* Bump maximum concurrent postgres connections

* More infra

* channels/jobs

* channels/app

* channels/api4

* Protect i18n from concurrent access

* Replace some use of os.Setenv

* Remove debug

* Lint fixes

* Fix more linting

* Fix test

* Remove use of Setenv in drafts tests

* Fix flaky TestWebHubCloseConnOnDBFail

* Fix merge

* [MM-62408] Add CI job to generate test coverage (#30284)

* Add CI job to generate test coverage

* Remove use of Setenv in drafts tests

* Fix flaky TestWebHubCloseConnOnDBFail

* Fix more Setenv usage

* Fix more potential flakyness

* Remove parallelism from flaky test

* Remove conflicting env var

* Fix

* Disable parallelism

* Test atomic covermode

* Disable parallelism

* Enable parallelism

* Add upload coverage step

* Fix codecov.yml

* Add codecov.yml

* Remove redundant workspace field

* Add Parallel() util methods and refactor

* Fix formatting

* More formatting fixes

* Fix reporting

server/channels/app/plugin_install_test.go

@@ -21,8 +21,7 @@ import (
 	"github.com/mattermost/mattermost/server/v8/channels/utils/fileutils"
 )
 
-type nilReadSeeker struct {
-}
+type nilReadSeeker struct{}
 
 func (r *nilReadSeeker) Read(p []byte) (int, error) {
 	return 0, io.EOF
@@ -69,6 +68,7 @@ func (b byBundleInfoID) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
 func (b byBundleInfoID) Less(i, j int) bool { return b[i].Manifest.Id < b[j].Manifest.Id }
 
 func TestInstallPluginLocally(t *testing.T) {
+	mainHelper.Parallel(t)
 	t.Run("invalid tar", func(t *testing.T) {
 		th := Setup(t)
 		defer th.TearDown()
@@ -268,6 +268,7 @@ func TestInstallPluginLocally(t *testing.T) {
 }
 
 func TestInstallPluginAlreadyActive(t *testing.T) {
+	mainHelper.Parallel(t)
 	th := Setup(t)
 	defer th.TearDown()