CAMEL-21336: Allow Kamelets configured by EnvVars only

[christophd]

Description

• Consider environment variables when validating Kamelet parameter configuration
• Avoids errors due to missing required Kamelet parameter validation when parameter is configured via environment variables

Target

• I checked that the commit is targeting the correct branch (note that Camel 3 uses camel-3.x, whereas Camel 4 uses the main branch)

Tracking

• If this is a large change, bug fix, or code improvement, I checked there is a JIRA issue filed for the change (usually before you start working on it).

See CAMEL-21336

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[davsclaus]

I think you should rename xxxEnvVar to be xxxEnvironmentVariable as that is the wording used elsewhere.