jextract: support Swift operators +/- etc

[ktoso]

Swift has custom operators like + etc, since Java doesn't have direct equivalent, today we drop them entirely.

Extracting

We need to start extracting operators; I think we can get them into ExtractedFunc and just give them a new .operator kind. Most of this work is done by SwiftAnalysisVisitor.

This would be done in the swift-extract layer; we should have tests that we extract all those kinds of operators.

Naming

Naming should likely have some recursive mechanism to give it a swift name ++ and we turn it into plusPlus etc. We should likely do this in makeJavaMethodName and have a special case for .operator apiKind there.

Swift	Java
+	plus
-	minus
*	times
/	dividedBy
%	remainder
<<	shiftedLeft
>>	shiftedRight
|	bitwiseOr
~	bitwiseNot
prefix -	negated
==	isEqual???
!=	isNotEqual
<	lessThan
<=	lessThanOrEqual
>	greaterThan
>=	greaterThanOrEqual
&	bitwiseAnd
^	bitwiseXor
??	coalescingNil
prefix !	logicalNot

There are some special ones, like == IF the type conforms to Equatable which translates to equals... so we'd probably skip that one because we already handle it as equals I think 🤔

And for printing I think this should mostly just work because they are effectively like functions.

Please also add runtime tests -- we do those by adding real examples in Samples/SwiftJavaExtractJNISampleApp/Sources/MySwiftLibrary (add an Operators.swift) and add a bunch of normal java Junit tests later on.