[chore] Update dependencies

[bitmovin-kenny]

Our dependencies were a bit outdated, so I updated all which did not cause severe problems.

The postcss-svg package upgrade from 1.0.6 to 3.0.0 changed the functionality by replacing url(relativePathToSvgFromScssFoder) instead of the previous svg(relativePathFromProjectRoot) so the scss files had to be updated.

We can't update the del package since it does not support require imports anymore, which we need in the gulpfile

Stuff I tested which still works:

• gulp
• gulp serve
• all UI variants in the playground
• older player versions with the updated UI

This PR drastically improves the output of npm i

• with this PR: 22 vulnerabilities (5 moderate, 14 high, 3 critical) (there are still some outdated minimist dependencies which i could not get rid of)
• on main branch: 40 vulnerabilities (9 moderate, 22 high, 9 critical)

also some deprecation warnings are no longer appearing:

npm WARN deprecated gulp-header@2.0.5: Removed event-stream from gulp-header
npm WARN deprecated clone@1.0.2: XSS vulnerability fixed in v1.0.3
npm WARN deprecated xmldom@0.1.19: Deprecated due to CVE-2021-21366 resolved in 0.5.0
npm WARN deprecated gulp-util@3.0.8: gulp-util is deprecated - replace it, following the guidelines at https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5
npm WARN deprecated buffer@4.9.1: This version of 'buffer' is out-of-date. You must update to v4.9.2 or newer
npm WARN deprecated svgo@0.5.6: This SVGO version is no longer supported. Upgrade to v2.x.x.