[Maps] User should be able to edit attribution (and potentially other details) of WMS, TMS layers

[kindsun]

With the addition of attribution options for WMS and TMS, it's easy to create a valid source but potentially enter the wrong attribution. Rather than requiring the user to remove and completely recreate the layer, we should add the ability to edit at least some, or potentially all, aspects of these layers.

[elasticmachine]

Pinging @elastic/kibana-gis

[nreese]

Closing, duplicate of #32821. Attribute needs to be moved from the source to layer so its available for all layers. Making it editable should be a part of that effort.