feat(java-dsl): Generate constructor documentation

[TimothyJones]

Fixes: amplication/amplication#9844

PR Details

This PR adds support for generating constructor documentation for Java.

• It uses the existing docs property for the parameters
• It adds an optional javadoc property to the Constructor type (the naming is consistent with the Class properties which also use javadoc)
• Tests are added for cases where parameters are documented but the constructor isn't, where the constructor is documented but the parameters aren't, and where both are documented

PR Checklist

• Tests for the changes have been added
• npm test doesn't throw any error

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