Load the spot hover icon when loading additional pointer resources

For hovering styluses, we want to explicitly show the "spot hover" icon
when the "show touches" feature is enabled. To do this, ensure we load
this icon style alongside other additional icon styles.

Also, maintain an explicit list of the additional icons to load, instead
of relying on the implicit ordering of the enum constants that are
defined elsewhere.

Bug: 342067371
Test: manual, enable "show touches" and "enable apps to show pointer
while hovering" settings
Flag: EXEMPT bug fix

Change-Id: I25bde3b974b5af1bd5ccea1561db1053b8acf3fb