Ignore the explicit names of READONLY properties when they are available

[bidorffOL]

Fix #2719

This PR uses the explicit names of READ_ONLY properties when they are available, otherwise it falls back to the current behavior of using their implicit name. This allows for the proper behavior of FAIL_ON_IGNORED_PROPERTIES on these properties.

[cowtowncoder]

Thank you very much for reporting the issue, submitting patch to fix it!
I will hope to review it soon.

One process thing that is needed before I can merge the fix is to get CLA (unless you have provided one already -- one is enough for all Jackson contributions). It can be found here:

https://github.com/FasterXML/jackson/blob/master/contributor-agreement.pdf

and usually is easiest to print, fill & sign, scan/photo, email to info at fasterxml dot com.
It is one-time only thing.

Thank you once again for your contribution!

[bidorffOL]

I just send it :)

Thank you for taking the issue into account !

[cowtowncoder]

Got the CLA, will merge this, backport, tweak a little bit -- can optimize lookup for just the READ_ONLY case, but will try to figure out why explicit name needed.

Thank you for the contribution!

[cowtowncoder]

Ah. So the explicit name is rename that has not yet applied, as removal is done first, before renaming, and so at this point name we'd have is the "implicit" one. That makes sense.
Will just need to see if I can refactor things to avoid unnecessary look-ups if possible (and perhaps check if implicit name should be added to ignorals too).