Upgrade supported Keycloak version to 22.x and 21.x

[engineering-issue-sync-app[bot]]

Related to https://github.com/camunda/product-hub/issues/1512

Description of the related problem to solve Keycloak releases a new major version every 3-6 months while dropping support for the older versions. This leads to unfixed security vulnerabilities found over time both in Keycloak and in it's libraries.

Describe a possible solution According to https://confluence.camunda.com/pages/viewpage.action?spaceKey=HAN&title=Camunda+8+Supported+Environments (TODO: document strategy there) in the next 8.3 release we should support Keycloak 22.0 and 21.1. Therefore we need to upgrade the libraries in our code, upgrade documentation and the default version in helm charts

Acceptance criteria

• [x] Identity uses Keycloak admin API libraries for Keycloak 22.0 and 21.1
• [x] The supported versions are updated in the compatibility matrix
• [x] #2045
• [x] #2046

Security considerations

E2E test cases

Additional context

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[engineering-issue-sync-app[bot]]

@MaxTru we are working on the issue with high priority. With my first analysis I assume that Keycloak 22.0 might not pick up the right configuration from our helm charts. @Ben-Sheppard will follow up with the distribution team to get it confirmed and fixed

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