ice: Expand use of VSI handles part 1/2

A VSI handle is just a number the driver maintains to uniquely identify
a VSI. A VSI handle is backed by a VSI number in the hardware. When
interacting when the hardware, VSI handles are converted into VSI numbers.

In commit 0f9d5027 ("ice: Refactor VSI allocation, deletion and
rebuild flow"), VSI handles were introduced but it was used only
when creating and deleting VSIs. This patch is part one of two patches
that expands the use of VSI handles across the rest of the driver. Also
in this patch, certain parts of the code had to be refactored to correctly
use VSI handles.

Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>