Trebuchet: Add 5x6, 5x7 and 6x6 default workspaces

  Had a 5x6 grid (with 6 hotseat spots) on my fajita back in los 16.0
  and wanted one on los 17.1
  On my Shamu I used to have 6x6 (with 6 hotseat spots)
  5x7 has 5 hotseat spots

Includes:
Author: Sam Mortimer <sam@mortimer.me.uk>
Date:   Sun May 16 21:26:44 2021 -0700

    Trebuchet: Set 5x6 grid to 5 hotseat icons

    * 5x5 and 5x7 have hotseat icon count 5 (matches column count)

    * 5x6 currently has hotseat icon count set to 6 which does not
      look good with the column count of 5.

    * The original commit message shows this was intentional:
      https://review.lineageos.org/q/Ib8d5dcc70d386376755c0a57b009ced1b2ee0834
      But a hotseat icon count of 5 for all of 5x5,5x6,5x7 looks more consistent.

    Change-Id: Ic55a258b8ef64d10b7440576af87d0e78d318cc3

Change-Id: Ib8d5dcc70d386376755c0a57b009ced1b2ee0834