Remove Claro dependency

All of Claro is now merged into Gin and all dependencies have been removed. Here is how I've done this:

• Assets from Claro (css, js, images) have been moved into a subdirectory merge of the Gin theme
• Libraries in gin.info.yml and gin.libraries.yml have been merged and updated
• The file claro.theme has been copied into Gin's include directory and duplicate hooks or preprocessors have been merged with those that already existed in Gin
• Templates have been merged into the templates directory by skipping those from Claro that were defined by Gin
• All remaining references to claro have been replaced with those to gin

Therefore, the MR has 513 changed files, i.e. this can not really be reviewed. My suggestion is to merge it as is after we've gone through some manual tests to see that everything appears to still be working. I noticed that minor pieces seem to be missing, and I hope that together we can iron them out and then merge this asap so that all other activities can be continued based on this groundwork.

jurgenhaas → credited saschaeggi → .

Managed to fix the final issues. The current status is that the MR renders the same result as before with Claro underneath.

As discussed with @saschaeggi I'm going to merge this so that we have the basis in the 6.x branch for further development. A review of the more than 500 added or changed files is pointless.

Automatically closed - issue fixed for 2 weeks with no activity.