chore(topology/uniform_space/basic): rename symmetric_rel_inter to …

…`symmetric_rel.inter` (#15441)

Also add `symmetric_rel.eq`

src/topology/uniform_space/basic.lean

@@ -195,12 +195,11 @@ lemma symmetric_rel.mk_mem_comm {V : set (α × α)} (hV : symmetric_rel V) {x y
   (x, y) ∈ V ↔ (y, x) ∈ V :=
 set.ext_iff.1 hV (y, x)
 
-lemma symmetric_rel_inter {U V : set (α × α)} (hU : symmetric_rel U) (hV : symmetric_rel V) :
+lemma symmetric_rel.eq {U : set (α × α)} (hU : symmetric_rel U) : prod.swap ⁻¹' U = U := hU
+
+lemma symmetric_rel.inter {U V : set (α × α)} (hU : symmetric_rel U) (hV : symmetric_rel V) :
   symmetric_rel (U ∩ V) :=
-begin
-  unfold symmetric_rel at *,
-  rw [preimage_inter, hU, hV],
-end
+by rw [symmetric_rel, preimage_inter, hU.eq, hV.eq]
 
 /-- This core description of a uniform space is outside of the type class hierarchy. It is useful
   for constructions of uniform spaces, when the topology is derived from the uniform space. -/
@@ -658,7 +657,7 @@ begin
   rw nhds_prod_eq,
   apply (has_basis_nhds x).prod' (has_basis_nhds y),
   rintro U V ⟨U_in, U_symm⟩ ⟨V_in, V_symm⟩,
-  exact ⟨U ∩ V, ⟨(𝓤 α).inter_sets U_in V_in, symmetric_rel_inter U_symm V_symm⟩,
+  exact ⟨U ∩ V, ⟨(𝓤 α).inter_sets U_in V_in, U_symm.inter V_symm⟩,
          ball_inter_left x U V, ball_inter_right y U V⟩,
 end