Move default fonts to new crate epaint_default_fonts (#4853)

This allows license checking tools to omit the OFL and UFL licenses when
`default_fonts` are turned off.

There was some discussion of versioning on the original issue; I have
chosen to label this version as `0.28.1` to match the other crates.
Happy to adjust the version as needed.

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* Closes <https://github.com/emilk/egui/issues/2321>
* [X] I have followed the instructions in the PR template

---------

Co-authored-by: Alex Pinkus <pinkus@amazon.com>

Cargo.lock

@@ -1444,6 +1444,7 @@ dependencies = [
  "document-features",
  "ecolor",
  "emath",
+ "epaint_default_fonts",
  "log",
  "nohash-hasher",
  "parking_lot",
@@ -1452,6 +1453,10 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "epaint_default_fonts"
+version = "0.28.1"
+
 [[package]]
 name = "equivalent"
 version = "1.0.1"