KT-5425 Kotlin plugin crashes when project uses RxJava 17.0 or older
 #KT-5425 Fixed
Initial version of storing SourceElements in descriptors

Introduce SourceElement, JavaSourceElementFactory, DeclarationDescriptorWithSource
Implement getSource() for eager, lazy and java descriptors
Rewrite BindingContextUtils.descriptorToDeclaration utilities family to use SourceElement for getting PSI

Remove DESCRIPTOR_TO_DECLARATION context key
Refactor: Remove context parameter from BindingContextUtils.descriptorToDeclaration utilities family
Drop SynthesizedCallableMemberDescriptor
Set source elements for java parameters
Set source elements for java enum entries

 #KT-4277 Fixed
Set source elements for java annotation parameters
Move descriptorToDeclaration utilities family to a separate util class DescriptorToSourceUtils
Fix usage of utility in KDoc
Restore check in BuiltInsReferenceResolver

Erroneously deleted in d98825683105e593ef34fbff780f6f84ecbc5162
Minor: Remove context parameter from getContainingFile() utility and move it to DescriptorToSourceUtils
Fix an NPE in VirtualFileKotlinClassFinder#findKotlinClass(JavaClass)

Happens for nonphysical PsiClass
Fix error message
Extracted test for "Join Lines" from CodeTransformationsTest.
Simplified CodeTransformationTest. Only one doTest method remains, intention class is moved to test data. Merged other intention tests (SpecifyTypeExplicitlyTest, ConvertToBlock/ExpressionBodyTest) into this one.
Renamed CodeTransformationTest -> IntentionTest.
KT-5397 Simplify text of DeMorgan law conversion intentions

 #KT-5397
Added test for KT-4827 UOE at PackageType.throwException()

 #KT-4827 obsolete
 #EA-53605 obsolete
KT-4980 'Remove braces' intention throws NPE for a for-loop with variable declaration

 #KT-4980 fixed