[C++][Gandiva] Fix nested if-else optimisation in gandiva

[asfimport]

In gandiva, when we have nested if-else statements we reuse the local bitmap and treat it is a single logical if - elseif - .. - --else condition. However, when he have say another function between them like
IF
THEN
ELSE
   function(
     IF
     THEN
     ELSE
  )

in such cases also currently we are doing same thing which can lead to incorrect results

Reporter: Projjal Chanda / @projjal
Assignee: Projjal Chanda / @projjal

PRs and other links:

• GitHub Pull Request #9486

_{Note: This issue was originally created as ARROW-11617. Please see the migration documentation for further details.}

[asfimport]

Praveen Kumar / @praveenbingo:
Issue resolved by pull request 9486
#9486