Modifies setters in AXNodeData to remove the attribute when set to None

1. Alphabetized all getters and setters in AXNodeData.
2. Setters in AXNodeData such as SetRestriction and SetTextDirection will now first check if the value is already set and remove it if so.
This will hopefully fix some of the duplicate values we have been seeing in the various attribute vectors.
Ultimately we would want to switch to using sets instead of vectors.
3. Changed to using base::EraseIf from base/stl_util.
R=aleventhal@chromium.org, dmazzoni@chromium.org

Also: 
Change-Id: Ib558d34e801a070d6b7f9d39680571030a8792cb
Reviewed-on: https://chromium-review.googlesource.com/c/1269078
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599421}

• ui/accessibility/BUILD.gn[diff]
• ui/accessibility/ax_node_data.cc[diff]
• ui/accessibility/ax_node_data.h[diff]
• ui/accessibility/ax_node_data_unittest.cc[Added - diff]