Bug fixes for about:bookmarks

[bsclifton]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Bug fixes for about:bookmarks:

• clear selection when click is outside of table
• clear selection when any element is dragged

Fixes #5223
Fixes #5249

NOTE: this updates appConfig to use about:newtab for new tabs if NODE_ENV=test, which is required for our tests to run. I had unintentionally broke those (because some tests rely on URL bar having focus) when submitting #5301

Auditors: @darkdh @bbondy

Test Plan:

1. Launch Brave and visit about:bookmarks
2. Import bookmarks or have bookmarks ready
3. Drag bookmarks from the view on the right over to a different folder
4. Observe that the selection is cleared
5. Use Ctrl or Cmd and select multiple items
6. Click below the table or click the header for the table
7. Notice the selection is cleared

[bbondy]

++

[darkdh]

++