Fix generation of JSON sample payload

[atextor]

Description

JSON sample payload generation sometimes includes a @type attribute that is
intentionally added to enable Jackson parsing JSON when Entity inheritance is
used. However, this is not valid according to the specification. This PR
therefore makes adding @type configurable with "off" being the default; in
addition it is possible to control the JsonTypeInfo annotation that is
inserted in generated Java classes; with the default now changed from NAME to
DEDUCTED (which works without @type in many cases), but it is changeable (in
Java API/Maven Plugin/samm-cli).

Fixes #669

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works

[Yauhenikapl]

LGTM!

[github-actions]

Release v2.9.8 addresses this.