Fix broken links to testcase definitions

Existing links to testcase definitions are broken after migration to QA report app.

The below links yield 404 not found. This is because the routes for the testcase definitions are under testcases/.

<release>/<testcase>.html
latest/<testcase>.html
<testcase>.html

Fix the broken links by,

<release>/<testcase>.html will 308 permanent redirect to testcases/<release>/<testcase>.html
latest/<testcase>.html will 307 temporary redirect to testcases/<default_branch>/<testcase>.html
<testcase>.html will 307 temporary redirect to testcases/<default_branch>/<testcase>.html

Fixes: https://phabricator.apertis.org/T9007