[llvm] [OpenMP] [IR Builder] Changes to Support Scan Operation (PR #136035)

[Anchu Rajendran S via llvm-commits]

anchuraj wrote:

> Instead of relying on `createScan` to be called withing the `BodyGen` callback, have you considered `createCanonicalScanLoops` to receive two callbacks: one for the input phase, and another for the scan phase?

Thank you @Meinersbur  for the review. I have tried to address the review comments. 
For the above comment, I  do not fully understand the design mentioned. I tried to create two lambdas in `ScanInfoInitialize` and stored it as two members (of type lambda) of the class `ScanInfo`, so the flang frontend calls these two lambdas when scan directive is lowered. However, that does not seem to simplify the design.  

https://github.com/llvm/llvm-project/pull/136035