[MNG-7193] Introduce MAVEN_ARGS environment variable

[michael-o]

Add args directly after the class name and leave users the option to override
with maven.config or CLI args.

This closes #637

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[rfscholte]

This needs to be documented somewhere as well.

[michael-o]

This needs to be documented somewhere as well.

You are right. I will locate the appropriate document before merging this.

[mthmulders]

Did the same test as three weeks ago but this time it behaves as expected 👍🏻

[mthmulders]

I guess this means we can close #602?

[michael-o]

I will supersede #602 with two alternative PRs.

[michael-o]

@rfscholte Updated inline scripts and add apache/maven-site#280.

[rfscholte]

Must also end up in https://github.com/apache/maven-wrapper

[michael-o]

@rfscholte While I agree those scripts are completely Maven 3. I.e, they would require to migrate to Maven 4 approach first. (reduced set). Cherry-picking pieces does not make sense. I can create a ticket to track this.