only check for url overflows when not hashing states

[spalger]

Fixes #10129

The url-overflow check ensures that the URL length doesn't get out of control and tries to warn users to use state hashing if the url is growing too long. Right now we still check the url length when the user has turned on state hashing, and since links to different states still use the unhashed state (so opening in a new tab still works, for instance) those urls trip the url-overflow check and cause Kibana to redirect to the url-overflow error page.

To prevent this I've added a check to the url-overflow check that ensures that state hashing is turned off before checking.

To reproduce this in master:

1. create a massive dashboard in chrome
2. try to open that dashboard in any IE/Edge
3. see the error
4. turn on state:storeInSessionStorage advanced config
5. visit the dashboard again and see the same error

In this PR the final step will actually render the dashboard.

[jbudz]

Is it expected for long urls pasted into IE/edge to throw a rison parse error instead of an overflow page in this case?

[spalger]

Pasting a URL will cause a risen parse error... hmm... but clicking a link from a wiki won't...

[epixa]

LGTM