Change the application access authentication flow

[ryanclark]

This is the frontend changes for this PR - gravitational/teleport#17592

This sets a custom X-Cookie-Value header on the request to /x-teleport-auth instead of putting it in the POST body.

We also remove a lot of the redirects (and the code that goes with it) as it's no longer required with the new authentication flow in the Teleport PR.

[ikkisoft]

LGMT. Comments left in #17592

[kimlisa]

We also remove a lot of the redirects (and the code that goes with it) as it's no longer required with the new authentication flow in the Teleport PR.

that means like url params like awsrole and state right? can we also delete useAppLaunder file since it doesn't look like it's being used. also does the backend PR delete the code that does the redirecting? eg redirectToLauncher, before I saw the above comment, i thought we missed these params

[ryanclark]

that means like url params like awsrole and state right? can we also delete useAppLaunder file since it doesn't look like it's being used. also does the backend PR delete the code that does the redirecting? eg redirectToLauncher, before I saw the above comment, i thought we missed these params

state is no longer needed - the backend changes remove the ?state= dance

arn is preserved and passed through to createAppSession if it's present (it was put into ?awsrole= during the redirects but we no longer need that)

I forgot about ?path= and have updated the PR to redirect to the given path if it's in the query params - nice catch!

I've also removed useAppLauncher