Modularise istgt_lu_disk_execute(CONN_Ptr, ISTGT_LU_CMD_Ptr)

[payes]

The following function istgt_lu_disk_execute(CONN_Ptr, ISTGT_LU_CMD_Ptr)https://github.com/openebs/istgt/blob/62d20a1ae272b4604359d47af06c1ff701f65033/src/istgt_lu_disk.c#L9072-L10923 can be refactored, which is a unit of 1537 lines of code.
Addressing this will make our codebase more maintainable and improve Better Code Hub's Write Short Units of Code guideline rating!

Here's the gist of this guideline:

• Definition 📖
  Limit the length of code units to 15 lines of code.
• Why❓
  Small units are easier to analyse, test and reuse.
• How 🔧
  When writing new units, don't let them grow above 15 lines of code. When a unit grows beyond this, split it in smaller units of no longer than 15 lines.

You can find more info about this guideline in Building Maintainable Software. 📖