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feat: add a SetLike default rule set for aesop (#7111)
This creates a new `aesop` rule set called `SetLike` to house lemmas about membership in subobjects.
Lemmas like `pow_mem` should be included in the rule set:
```lean
@[to_additive (attr := aesop safe apply (rule_sets [SetLike]))]
theorem pow_mem {M A} [Monoid M] [SetLike A M] [SubmonoidClass A M] {S : A} {x : M}
(hx : x ∈ S) : ∀ n : ℕ, x ^ n ∈ S
```
Lemmas about closures, like `AddSubmonoid.closure` should be included in the rule set, but they should be assigned a penalty (here we choose `20` throughout) so that they are not attempted before the general purpose ones like `pow_mem`.
```lean
@[to_additive (attr := simp, aesop safe 20 apply (rule_sets [SetLike]))
"The `AddSubmonoid` generated by a set includes the set."]
theorem subset_closure : s ⊆ closure s := fun _ hx => mem_closure.2 fun _ hS => hS hx
```
In order for `aesop` to make effective use of `AddSubmonoid.closure` it needs the following new lemma.
```lean
@[aesop 5% apply (rule_sets [SetLike])]
lemma mem_of_subset {s : Set B} (hp : s ⊆ p) {x : B} (hx : x ∈ s) : x ∈ p := hp hx
```
Note: this lemma is marked as very unsafe (`5%`) because it will apply *whenever* the goal is of the form `x ∈ p` where `p` is any term of a `SetLike` instance; and moreover, it will create `s` as a metavariable, which is in general a terrible idea, but necessary for the reason mentioned above.
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