Add Java 21 Support to Side projects

[psavidis]

Acceptance Criteria (Required on creation)

Java 21 is available as a build environment and by the following repositories:

• [x] camunda-spin
• [x] camunda-connect
• [x] camunda-commons
• [x] camunda-template-engines-jsr223
• [x] feel-scala

Note: camunda-bpm-rpa-bridge-ee will be considered out of scope for the 7.21 release.

Hints

• The respective Jenkins stages (declaration and use) need to be added in .ci.cambpm file

Links

• Parent Issue
• Infra Issue for making Java 21 available to be consumed by Jenkins builds.

Breakdown

### Upstream and Other Projects PR
- [ ] https://github.com/camunda/camunda-spin/pull/215
- [ ] https://github.com/camunda/camunda-connect/pull/87
- [ ] https://github.com/camunda/camunda-commons/pull/39
- [ ] https://github.com/camunda/camunda-template-engines-jsr223/pull/36
- [ ] https://github.com/camunda/feel-scala/pull/803
- [ ] https://github.com/camunda/feel-scala/pull/808

[yanavasileva]

@psavidis, please note that Status must be Review when requesting a review.

[yanavasileva]

@psavidis, feel scala change must be backported to the minor version branch that currently is used by Camunda 7.21, which is 1.16. Reference: https://github.com/camunda/camunda-bpm-platform/blob/master/pom.xml#L35 Hint: feel scala repo uses the backport action.

[psavidis]

@psavidis, feel scala change must be backported to the minor version branch that currently is used by Camunda 7.21, which is 1.16. Reference: https://github.com/camunda/camunda-bpm-platform/blob/master/pom.xml#L35 Hint: feel scala repo uses the backport action.

Thanks for the reminder Yana. Following a discussion with Tassilo, it makes sense to backport JDK 21 config to the 1.7 branch as a newer release and update the repo to point to the latest patch version (that would be 1.17.5).

[tasso94]

Related to bumping the FEEL Engine 1.17.5: https://github.com/camunda/camunda-bpm-platform/issues/4075