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/repo_webhook_test.go

@@ -316,6 +316,7 @@ func assertInput(t testing.TB, form *goquery.Selection, name string) string {
 
 func testWebhookForms(name string, session *TestSession, validFields map[string]string, invalidPatches ...map[string]string) func(t *testing.T) {
 	return func(t *testing.T) {
+		defer tests.PrintCurrentTest(t)()
 		t.Run("repo1", func(t *testing.T) {
 			testWebhookFormsShared(t, "/user2/repo1/settings/hooks", name, session, validFields, invalidPatches...)
 		})