[Waste] Limit image size on Echo backed Bulky Collection reports.

[neprune]

[skip changelog]

closes https://github.com/mysociety/societyworks/issues/4243

mysoc-servers branch: gh-4243.

Verified on staging with a load of 4.7MB 2048x2048 jpegs: https://bromley.staging.fixmystreet.com/admin/report_edit/24439.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 31.42857% with 24 lines in your changes are missing coverage. Please review.

Project coverage is 82.66%. Comparing base (3adcce8) to head (49b1501).

:exclamation: Current head 49b1501 differs from pull request most recent head 4afb9b8. Consider uploading reports for the commit 4afb9b8 to get more accurate results

Files	Patch %	Lines
perllib/FixMyStreet/App/Model/PhotoSet.pm	0.00%	17 Missing :warning:
perllib/FixMyStreet/Roles/CobrandEcho.pm	66.66%	0 Missing and 5 partials :warning:
perllib/FixMyStreet/ImageMagick.pm	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4939 +/- ## ========================================== + Coverage 82.61% 82.66% +0.04% ========================================== Files 391 392 +1 Lines 30488 30749 +261 Branches 4813 4868 +55 ========================================== + Hits 25189 25419 +230 - Misses 3865 3887 +22 - Partials 1434 1443 +9 ```

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[neprune]

@dracos I still need to write tests for some coverage but sharing in case you have an early feedback.

[neprune]

@dracos Added some tests now, ready for review.