fix: LEAP-89: Fix rendering of relation arrow in MIG case

[Gondragos]

PR fulfills these requirements

• [x] Commit message(s) and PR title follows the format [fix|feat|ci|chore|doc]: TICKET-ID: Short description of change made ex. fix: DEV-XXXX: Removed inconsistent code usage causing intermittent errors
• [ ] Tests for the changes have been added/updated (for bug fixes/features)
• [ ] Docs have been added/updated (for bug fixes/features)
• [x] Best efforts were made to ensure docs/code are concise and coherent (checked for spelling/grammatical errors, commented out code, debug logs etc.)
• [x] Self-reviewed and ran all changes on a local instance (for bug fixes/features)

Change has impacts in these area(s)

(check all that apply)

• [ ] Product design
• [x] Frontend

Describe the reason for change

In the case of Image Segmentation with Image tag being in gallery mode a relation arrow may not follow the regions on switching between images.

What does this fix?

It adds an directive for relation to observe current image index to initiate rendering of an arrow on switching between images.

What libraries were added/updated?

N/A

Does this change affect performance?

Nope

Does this change affect security?

Nope

What alternative approaches were there?

N/A

What feature flags were used to cover this change?

N/A

Does this PR introduce a breaking change?

(check only one)

• [ ] Yes, and covered entirely by feature flag(s)
• [ ] Yes, and covered partially by feature flag(s)
• [x] No
• [ ] Not sure (briefly explain the situation below)

What level of testing was included in the change?

(check all that apply)

• [ ] e2e
• [ ] integration
• [ ] unit

Which logical domain(s) does this change affect?

Image Segmentation, Image, Relations, Gallery

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (bee2622) 68.28% compared to head (b4ebb3d) 68.28%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1631 +/- ## ======================================= Coverage 68.28% 68.28% ======================================= Files 443 443 Lines 28687 28687 Branches 7629 7629 ======================================= + Hits 19589 19590 +1 + Misses 7846 7845 -1 Partials 1252 1252 ```

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