Make Definitions agree with the enum about tool order

[SimonCropp]

Both files carry a "keep in sync" comment and they had drifted in two places:
TortoiseMerge sat before the TortoiseGit pair in the enum and after it in
Definitions, and the enum had VisualStudio before Cursor while Definitions had
them the other way round.

That matters because the two lists are used for different things. The enum is
the default resolution order - OrderReader hands back Enum.GetValues - while the
generated docs and the remainder after a DiffEngine_ToolOrder prefix follow
Definitions. So the published order was not the order tools actually resolve in,
and a user reading the docs to pick a prefix was reading the wrong list.

Definitions moves to match the enum, since the enum is what actually decides.
Generated docs regenerated to match.

The test that exists to catch this could not: IsEquivalentTo is order
insensitive by default, so it passed on both lists. IsEqualTo is no good either

• on two lists it compares references - so the assertion joins them, which is
  order sensitive and names the first tool that differs instead of reporting that
  the contents match.