interpreter: use typed_kwargs for jar(java_resources)

With the added bonus of adding the correct `since` checking values!

mesonbuild/interpreter/kwargs.py

@@ -354,3 +354,4 @@ class BuildTarget(Library):
 class Jar(_BaseBuildTarget):
 
     main_class: str
+    java_resources: T.Optional[build.StructuredSources]

mesonbuild/interpreter/type_checking.py

@@ -10,7 +10,7 @@ import typing as T
 from .. import compilers
 from ..build import (CustomTarget, BuildTarget,
                      CustomTargetIndex, ExtractedObjects, GeneratedList, IncludeDirs,
-                     BothLibraries, SharedLibrary, StaticLibrary, Jar, Executable)
+                     BothLibraries, SharedLibrary, StaticLibrary, Jar, Executable, StructuredSources)
 from ..coredata import UserFeatureOption
 from ..dependencies import Dependency, InternalDependency
 from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo
@@ -534,6 +534,7 @@ SHARED_MOD_KWS = [
 # them into build_target easier
 _EXCLUSIVE_JAR_KWS: T.List[KwargInfo] = [
     KwargInfo('main_class', str, default=''),
+    KwargInfo('java_resources', (StructuredSources, NoneType), since='0.62.0'),
 ]
 
 # The total list of arguments used by JAR