[Public map] UX improvements

[VictorVelarde]

From 0.1 tests, we detected:

• [ ] Improve the style of the selected provider
• [ ] Clean shared url textbox when closing window
• [ ] Change the "Upload copy"? --> have some specific copy for Carto, instead of the generic current one
• [ ] Missing icons in staging for Github / Google when using OAuth2

[ana-md]

I am closing this old issue, but @MireyaD let's keep this in mind as it came up in our previous test and:

• If it is solved now --> OK
• If not --> Let's add it to the QA findings summary