Fix issue where the parser can read back old number state when parsing later numbers

[pjfanning]

• new version of try to fix issue where _numberString is used despite having old value #1389 but targeted at 2.17 branch
• only the original test in test for issue #4917 jackson-databind#4918 is affected by the bug - similar tests (V2, V3, etc) are not affected.
• Aim is to use this fix for patch releases but to later try a bigger change to better manage number state in the parser code - in the 2.19 development branch

[cowtowncoder]

Ok that sounds reasonable. One reason why I think this fix is not ideal is that it actually does not clear the state unless value is accessed -- so it just covers this specific case and not others. But at the same it is somewhat minimal fix which is a plus for patch releases.

[cowtowncoder]

Hmmmh. Playing with tests, the only fix that has any effect here is in getDoubleValue(), line 864. But it looks like _numberString is actually being cleared via convertNumberToDouble() which calls _getNumberDouble() where _numberString is actually cleared.

I think I'll trim down changes slowly to parts that seem useful in general (namely, immediate return after "convertXxx()" calls). And then look into 2.19 for more general clearing.

[cowtowncoder]

Merged all the way to master: for 2.19 and master has clearing of _numberString on reset[Number]() methods as safeguard.

Thank you for test & fix @pjfanning !