chore: improve slow tests

- Optimize generting random files.
- Reduce big file of 128MiB to 32MiB (git was never made for large files
anyways, but simply tests that it works).
- Reduce looped git operations from 100 iterations to 10.
- Add extra print statements to know what a slow test is doing, this
also helps to see if a particular piece of code in a slow test is the
culprit or if the test is just very extensive.
- Set `[ui.notification].EVENT_SOURCE_UPDATE_TIME` to 1s to speed up
`TestEventSourceManagerRun`.
- Sneaked in some general test improvements.

tests/integration/cmd_admin_test.go

@@ -10,6 +10,7 @@ import (
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/tests"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -44,6 +45,7 @@ func Test_Cmd_AdminUser(t *testing.T) {
 			},
 		} {
 			t.Run(testCase.name, func(t *testing.T) {
+				defer tests.PrintCurrentTest(t)()
 				name := "testuser"
 
 				options := []string{"user", "create", "--username", name, "--password", "password", "--email", name + "@example.com"}