Allow for marketplace provided plugin cover images

[michalkleiner]

Description:

The change in this PR allows for use of cover images provided by the plugins marketplace while keeping the existing fallback images for Matomo vs 3rd party plugins.

The PR:

• adds a mechanism to display a cover image specified in the plugin's metadata
• tweaks the existing fallback logic so that all paid Matomo plugins without a cover image use the blue Matomo image and all other free plugins regardless of their vendor use the generic grey plugin image
• adds a mechanism via the test config to replace remote image URLs with local test image URLs for UI tests
• updates file formatting for all static marketplace fixtures for better legibility

There is also a follow-up draft PR #21915 which should be merged once the corresponding changes to the marketplace have been deployed so that the test there can pass.

ref. DEV-17378

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

[michalkleiner]

Failure for Piwik\Plugins\Marketplace\tests\System\Api\ClientTest::test_getPluginInfo_existingPluginOnTheMarketplace within the SystemTestsPlugins suites (for all 3 PHP versions) is expected until a corresponding change providing the category and coverImage fields is deployed to the marketplace.

I'd be happy to remove the change to the test and add it back after the marketplace change is deployed to production if that's preferred.

UPDATE: Discussed in person with MC and will move this to a separate PR that can be merged once the corresponding change is deployed to Marketplace PROD.

UPDATE 2: Moved to PR #21915

[michalkleiner]

This change can be reviewed, merged and released independently of the marketplace changes as it provides defaults for the category and cover image in the same way how it worked before.

[michalkleiner]

Thanks @sgiehl. I know we don't want dead code that won't be used though I'm confident this will get through at the Marketplace end as well. Also, the change surface here is quite contained, so I think this can be merged. If we need to adjust anything I can follow up on that.