add rosling bubbles test

[aakritixyz]

i'm adding test-renderer-rosling-bubbles.R to verify interactive bubble plots.

local Verification:
my previous test video didn't utilize the internal Chromote functions. I have now refactored the environment to use a Chromote backend, allowing for a post-JS rendered DOM capture.

updated Video Demo: [https://youtu.be/F5YkaAXtUbo]

@suhaani-agarwal, @tdhock please review the test logic. I have also patched the tests_init() helpers locally to support this Chromote workflow; let me know if those should be included here or in a separate PR.

[tdhock]

the test looks ok, but you should remove those functions.

[aakritixyz]

@tdhock,
I have updated the PR to remove the internal helper functions and overrides as suggested.

[suhaani-agarwal]

@suhaani-agarwal, @tdhock please review the test logic.

the test looks good and aligns with the GSoC evaluation requirements.

From my understanding, similar svg-rendering checks already exist in other test-renderer-* files, so this may not add new coverage, but it does show a clear understanding of the animint2 testing workflow.
If you’d like to explore further, you could try extending the test to validate interactive behaviours (e.g., tooltips, clickSelects, or dynamic year transitions).

[aakritixyz]

@suhaani, thanks for the feedback!

i’ve updated the test to use the new parameter-based syntax for showSelected and clickSelects. i also extended it to validate interactive elements like the Play/Pause widgets and selection attributes.