feat(console-plugin): uninstall plugin when upgrading Cryostat on unsupported OCP version

[andrewazores]

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Fixes: #1259

Description of the change:

1. Enhances the OpenShift Console Plugin installation check to additionally check if the current cluster version is below the minimum supported version. Previously the logic was a simple one-way "if version >= minimum, install plugin." Now there is an "else, uninstall plugin" branch. This covers the case where Cryostat/cryostat-web/cryostat-openshift-console-plugin are upgraded in a way that increases the required Console version compared to the previous Cryostat version. If a Cryostat installation on a given OpenShift cluster is upgraded and the cluster itself is not upgraded, then it's possible that some features will no longer be available and should be disabled/removed.
2. Sets the minimum OpenShift version to 4.19 - see https://github.com/openshift/console/blob/main/frontend/packages/console-dynamic-plugin-sdk/README.md#patternfly, chore(patternfly): upgrade to Patternfly 6 cryostat-web#2137, chore(deps): update patternfly (major) cryostat-openshift-console-plugin#833, [Task] Investigate what PF stylesheets are provided by each version of the Console cryostat-openshift-console-plugin#128, and CONSOLE-5100: Remove support for PatternFly 5 openshift/console#16056
3. Refactors the OpenShift version value from a hardcoded constant in the source code to an environment variable which can be set at build time. This helps consolidate all the versions to be updated into the Makefile.
4. According to https://access.redhat.com/product-life-cycles?product=OpenShift%20Container%20Platform%204 , OpenShift 4.19 is currently in Maintenance support. 4.20 and 4.21 are the current fully supported versions but 4.22, the first version which will ship exclusively supporting Patternfly 6, will be coming soon.

How to manually test:

1. Insert steps here...
2. ...

[andrewazores]

/build_test

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