[HttpFoundation] [Request] prepareBaseUrl doesn't compare URL case-insensitivly

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -


If the comparison between SCRIPT_FILENAME and SCRIPT_NAME isn't case-insensitive
then accessing /App.php/myroute or /aPP.php/myroute won't work, and we will always have to verify accessing
/app.php/myroute (with app at lower case, which may cause many problems).