Refactor integration tests infrastructure (#37462)

Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/sqlite.ini.tmpl

@@ -1,4 +1,4 @@
-WORK_PATH = {{WORK_PATH}}
+WORK_PATH = {{TEST_WORK_PATH}}
 APP_NAME = Gitea: Git with a cup of tea
 RUN_MODE = prod
 
@@ -88,7 +88,7 @@ ENABLED = true
 [markup.html]
 ENABLED = true
 FILE_EXTENSIONS = .html
-RENDER_COMMAND = go run tools/test-echo.go
+RENDER_COMMAND = go run {{GITEA_TEST_ROOT}}/tools/test-echo.go
 ;RENDER_COMMAND = cat
 ;IS_INPUT_FILE = true
 RENDER_CONTENT_MODE = sanitized
@@ -96,7 +96,7 @@ RENDER_CONTENT_MODE = sanitized
 [markup.no-sanitizer]
 ENABLED = true
 FILE_EXTENSIONS = .no-sanitizer
-RENDER_COMMAND = go run tools/test-echo.go
+RENDER_COMMAND = go run {{GITEA_TEST_ROOT}}/tools/test-echo.go
 ; This test case is reused, at first it is used to test "no-sanitizer" (sandbox doesn't take effect here)
 ; Then it will be updated and used to test "iframe + sandbox-disabled"
 RENDER_CONTENT_MODE = no-sanitizer