Previously, clicking on the same workspace you were on would throw you
to another workspace if `workspace_auto_back_and_forth yes` was
specified in your sway config. This also fixes workspace output moving
misbehaving and doing the same.
The approximation should include SReclaimable, and subtract Shmem. To
prevent the parsing code from ballooning in size, this commit also
refactors the parsing into a map.
Tudor Brindus