Make dynamic plugin dependencies optional

[vojtechszocs]

• Plugin metadata field dependencies is now optional.
• Plugin dependency @console/pluginAPI is now optional. If missing, the Console version check is skipped.
• Existing plugins with @console/pluginAPI dependency (regardless of version range used) are not affected.
• Removed @console/pluginAPI dependency from dynamic demo plugin.
• Updated README to account for semver pre-release specifics when declaring plugin dependencies.

[vojtechszocs]

/retest

[vojtechszocs]

QE Approver: /assign @yapei

Docs Approver: /assign @opayne1

PX Approver: /assign @RickJWagner

Console Approver: /assign @jhadvig

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jhadvig, vojtechszocs

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Needs approval from an approver in each of these files:

• ~~dynamic-demo-plugin/OWNERS~~ [jhadvig,vojtechszocs]
• ~~frontend/packages/console-dynamic-plugin-sdk/OWNERS~~ [jhadvig,vojtechszocs]

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[RickJWagner]

/label px-approved

[opayne1]

@jhadvig is this another one we need to update from plugin to plug-in? I am going to go ahead and add the label though.

[opayne1]

/label docs-approved

[yapei]

QE tested the changes, confirmed that plugin metadata fielddependencies is now optional(plugin still work without dependencies) and no regressions(existing plugins with dependencies still work) /label qe-approved