New binding for magit-file-dispatch is confusingly different from magit-dispatch binding

[ilyagr]

Recent commit e3434e8 switched the <SPC> g f d binding to mean magit-file-dispatch instead of magit-file-diff. I'm very happy to have a binding for magit-file-dispatch. However, now there is a confusing mismatch: <SPC> g f d means magit-file-dispatch, and <SPC> g m means magit-dispatch. I think one of the following two things should happen:

a) <SPC> g f m should mean magit-file-dispatch and <SPC> g f d should be restored to mean magit-file-diff. I'd prefer this, since magit-file-diff is useful.

b) The binding to magit-dispatch should change to <SPC> g d.

If either of these options look OK, I'm happy to implement it.

[ilyagr]

See also #14408 for background. I don't think anyone noticed the mismatch.

[lebensterben]

I prefer the first solution.