Tree Tent test improvements

[charlestian23]

Just reposting some of the improvements we can make to Tree Tent:

TooFewTents: Using a 1x1 board might be an edge case itself ... I would add a test case with a 2x2 or 3x3 board where the contradiction occurs in only one or some of the columns or rows ... analogous to what you do with testing TooManyTents

For any of the contradiction rules: please make sure you test for incorrect or 'false' applications of those rules, i.e. that LEGUP correctly responds by saying that some contradiction rule does not check out ... because there is indeed no contradiction of the kind that the contradiction rule is supposed to point out.

Same with Direct rules: make sure to have test cases where the Direct rule application should not check out

Starting with FinishWithGrass: please comment test cases

Originally posted by @Bram28 in #683 (review)