Remove singleTask from Settings homepage

Launch Settings homepage on a NO ActivityEmbedding supported device:

  Before & after this change, launch Settings homepage will resume
an existing Settings task and finish SubSettings on top of Settings
homepage.

Launch Settings homepage on a ActivityEmbedding supported device:

  Before this change, launch Settings homepage will resume
an existing Settings task and finish SubSettings on top of Settings
homepage and then start SubSettings.

  After this change, launch Settings homepage will resume
an existing Settings task and resume existing SubSettings.

This change improves UX (keep right pane Activity status) and improves
launch performance (it will not finish and start right pane Activity)
for ActivityEmbedding supported devices.

Bug: 240666118
Test: manual
      Launch Settings and observe events log.
Change-Id: I226b852b360e7106e861752d748f644596a0f320