Manage dependency on Material in attribution widgets

[JaffaKetchup]

The only remaining components in the library that use actual material components are the attribution layers:

• The simple attribution widget uses Theme to set its background colour
• The logo source uses a Tooltip - RawTooltip is available from Flutter 3.41 (flutter/flutter@6679464)
• The rich attribution widget uses it extensively for buttons, etc. I have not checked for buttons in the new raw widget library, maybe they will be in there.

There is no rush to move over to material_ui yet necessarily. But we should look into decoupling these from material wherever possible. There's multiple options, all breaking:

• Remove anything which can't be converted to not depend on material or cupertino from the core library
• As a half-way option, convert every widget builder to take an external builder, leaving it to the user to build the button, for example - personally, I prefer this option most, but at what point is what's left so barebones that it doesn't make sense to keep it
• Just go ahead and use material_ui

One option I'm considering is deprecating and eventually removing RichAttributionWidget and keeping (and slightly improving) the SimpleAtrributionWidget only. Or, deprecate the existing rich widget and create a v2 which requires the builders mentioned in the second option above.

Note that using material_ui will also require flutter_map's minimum SDK support to be raised to Flutter 3.44, which may or may not be unacceptable.