feat(feel): added backoff FEEL function for exponential backoff with jitter

[azan-baloch]

Description

added backoff feel function for computing exponential backoff with jitter.
Tested with REST connector and get expected result(increasing delay),
51ms → 76ms → 130ms → 197ms → 343ms

Here's screenshot of logs

SS of feel expression

Related issues

closes #6710

Checklist

• Backport labels are added if these code changes should be backported. No backport label is added to the latest
  release, as this branch will be rebased onto main before the next release. Example backport labels:
  • backport stable/8.8: for changes that should be included in the next 8.8.x release.
  • or backport release-8.8.7: for changes that should be included in the specific release 8.8.7, and this
    release has already been created. The release branch will be merged back into stable/8.8 later, so the change
    will be included in future 8.8.x releases as well.
• Tests/Integration tests for the changes have been added if applicable.
• If the change requires a documentation update, it has been added to the appropriate section in the documentation.

[azan-baloch]

Moved each function into its own class under function subpackage and also created shared helper class FunctionHelper. Let me know if anything needs changes.

[johnBgood]

Thank you again for your contribution 🥇

[ztefanie]

I just pinged qa for testing.