Add AnnotationIntrospector.findRenameByField() to support Kotlin's "is-getter" naming convention

[cowtowncoder]

(note: follow up for FasterXML/jackson-module-kotlin#80)

So, Kotlin generates its property accessors, fields similar to (but not identical) Bean conventions:

https://kotlinlang.org/docs/reference/java-to-kotlin-interop.html

and as a result Jackson's default introspection has some trouble, in particular for "is getters".
While there is now a patch for Kotlin, it might make sense to add a MapperFeature to enable it at lower level -- both for being bit more optimal, and to avoid possible regression when databind introspection changes in future (for 3.0 in particular).

[cowtowncoder]

Note: filed #2571 as something that might solve this with more general mechanism.

[cowtowncoder]

After wrestling with this for a bit -- trying not to add a new (too) specific MapperFeature, but also not wanting to add yet another handler for single use case either -- decided on something in-between: introduce a new introspection method in AnnotationIntrospector, with handling that does clean renaming, and a unit test that emulates how I think Kotlin runtime works.

Will need to verify with jackson-module-kotlin itself too, of course.