Drop AnnotationUsage#getAttributeValue overloads accepting defaults

[sebersole]

Drop the following methods:

• getAttributeValue(String name, V defaultValue)
• getAttributeValue(String name, Supplier defaultValueSupplier)
• getString(String name, V defaultValue)
• getString(String name, Supplier defaultValueSupplier)
• ...

Those were useful in the initial iterations where an attribute's default value was stored internally as null to indicate that no value was specified.

However it was decided later during development that this should follow the JDK pattern of "not specified" equating to the default value being stored. Therefore, a null check to return the passed in defaultValue is pointless.

[sebersole]

This is fixed by a30b9695ce0dbe53010f5a39b7f71dcd9531bd8a. IntelliJ's new Git dialog is just confusing..