Using sub-arrays in the scan function results in undefined behaviour in the oneapi backend.

Description

The offsets were not taken into account in the oneapi code.

28bd6b0 : adds the the function toTempFormat to the test helpers. This function generates the different temporary array formats (JIT array, SUB-array, Linear array, ...) used by arrayfire.
6fe4646 : Adds the offset to the cl code files & adds extra tests for scan.

• Is this a new feature or a bug fix?
  BUG
• Why these changes are necessary.
  PREVIOUSLY THE RESULT IS UNDEFINED FOR ABOVE SITUATION
• Potential impact on specific hardware, software or backends.
  ONEAPI only
• New functions and their functionality.
  NO
• Can this PR be backported to older versions?
  YES, changes are very local
• Future changes not implemented in this PR.
  NONE, although the function toTempFormat will be used in following PRs.

Changes to Users

None

Checklist

• Rebased on latest master
• Code compiles
• Tests pass
• Functions added to unified API
• Functions documented