Some Slices API refinement

Removing overloads, fixing documentation, adding stringdefs, etc.

Test: update-api
Change-Id: Iae902092a29d44c3f4735ad2c3392bb35988684a
Fixes: 73124159
Bug: 73123366
Fixes: 73123451
Fixes: 73123651
Fixes: 73124123
4 files changed