[a11y] Put the image name in the alt attribute of the thumbnail on the metadata page

[MichelGabriel]

This commit adds the <img> in the alt attribute when there is a name, otherwise a default string is used.

The image name used to be the caption underneath the thumbnail, but is now removed

Extra: the max-height is increased in order to have the full width of the image.

Checklist

• I have read the contribution guidelines
• Pull request provided for main branch, backports managed with label
• Good housekeeping of code, cleaning up comments, tests, and documentation
• Clean commit history broken into understandable chucks, avoiding big commits with hundreds of files, cautious of reformatting and whitespace changes
• Clean commit messages, longer verbose messages are encouraged
• API Changes are identified in commit messages
• Testing provided for features or enhancements using automatic tests
• User documentation provided for new features or enhancements in manual
• Build documentation provided for development instructions in README.md files
• Library management using pom.xml dependency management. Update build documentation with intended library use and library tutorials or documentation

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[josegar74]

Tested, works fine.