Set up an error page when the token could not be validated.

[Vlatombe]

When using Token Field Key To Check and Token Field Value To Check to restrict login access to an instance, if a user that doesn't match the specified criteria, you get a HTTP 401 error

This introduces a nicer error page, providing a link to log out from the OpenID Connect Provider (if configured).

Testing done

Tested manually with a configured Token Field Key To Check/Token Field Value To Check and combinations where the user matches the token field or doesn't match it.

Submitter checklist

• [X] Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• [X] Ensure that the pull request title represents the desired changelog entry
• [X] Please describe what you did
• [ ] Link to relevant issues in GitHub or Jira
• [ ] Link to relevant pull requests, esp. upstream and downstream changes
• [ ] Ensure you have provided tests - that demonstrates feature works or fixes the issue

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.

Project coverage is 73.59%. Comparing base (bca3705) to head (134c292). Report is 6 commits behind head on master.

Files	Patch %	Lines
...va/org/jenkinsci/plugins/oic/OicSecurityRealm.java	95.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #344 +/- ## ============================================ + Coverage 72.46% 73.59% +1.12% - Complexity 201 209 +8 ============================================ Files 9 10 +1 Lines 839 852 +13 Branches 119 120 +1 ============================================ + Hits 608 627 +19 + Misses 170 163 -7 - Partials 61 62 +1 ```

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[Vlatombe]

@michael-doubez This is ready to be reviewed