Add error logging to extractor

[teabot]

What problem are you facing?

When selectors fail to resolve values correctly (see crossplane-contrib/provider-upjet-aws#118), it is hard to diagnose the probable issue.

How could Upjet help solve your problem?

It would be beneficial to add some additional logging in extractor.go to log errors, which are currently swallowed silently:

• https://github.com/crossplane/upjet/blob/1644827c946b45e8087d003b0ae21c8a73bab027/pkg/resource/extractor.go#L47-L50
• https://github.com/crossplane/upjet/blob/1644827c946b45e8087d003b0ae21c8a73bab027/pkg/resource/extractor.go#L53-L56