Try to make AlgClosureFp tests fail less often

Instead of using the global cached versions of the starting fields,
use fresh copies to avoid interference by the global effects of
previous tests.

Of course this does not solve the fundamental issue, but for now
it should reduce the number of times CI fails randomly due to this.

test/Rings/AlgClosureFp.jl

@@ -5,12 +5,12 @@ function test_elem(K::AlgClosure{T}) where T <: FinField
 end
 
 @testset "AlgClosureFp" begin
-  @testset "Interface for $F" for F in [GF(3, 1), Nemo._GF(3, 1)]
-    K = algebraic_closure(GF(3,1))
+  @testset "Interface for $F" for F in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
+    K = algebraic_closure(F)
     test_Field_interface(K)
   end
 
-  @testset "Creation for $F" for F in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Creation for $F" for F in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F)
     @test base_field(K) === F
     @test characteristic(K) == characteristic(F)
@@ -52,7 +52,7 @@ end
     @test a == b
   end
 
-  @testset "Printing for $F" for F in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Printing for $F" for F in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F)
     @test sprint(show, "text/plain", K) == "Algebraic Closure of Finite field of degree 1 over GF(3)"
 
@@ -61,7 +61,7 @@ end
     end
   end
 
-  @testset "Coercion and conversion for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Coercion and conversion for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F1)
     F2 = ext_of_degree(K, 2)
     a = gen(F2)
@@ -74,7 +74,7 @@ end
     @test_throws ErrorException F2(d)
   end
 
-  @testset "Arithmetic for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Arithmetic for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F1)
     @test is_unit(K(one(F1)))
     @test !is_unit(zero(K))
@@ -103,7 +103,7 @@ end
     end
   end
 
-  @testset "Ad hoc operations for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Ad hoc operations for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F1)
     for i in 1:10
       a = test_elem(K)
@@ -122,7 +122,7 @@ end
     end
   end
 
-  @testset "Comparison for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Comparison for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F1)
     F2 = ext_of_degree(K, 2)
     F3 = ext_of_degree(K, 3)
@@ -136,7 +136,7 @@ end
     @test hash(K(one(F2)), zero(UInt)) == hash(K(one(F3)), zero(UInt))
   end
 
-  @testset "Embeddings for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Embeddings for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     K = algebraic_closure(F1)
     F2 = ext_of_degree(K, 2)
     F3 = ext_of_degree(K, 3)
@@ -151,7 +151,7 @@ end
     @test !has_preimage(emb, K(gen(F3)))[1]
   end
 
-  @testset "Polynomial for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Polynomial for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     p = characteristic(F1)
     K = algebraic_closure(F1)
     Kx, x = K["x"]
@@ -161,7 +161,7 @@ end
     @test sort!(map(degree, r)) == [1, 1, 2, 2]
   end
 
-  @testset "Matrix for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Matrix for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     p = characteristic(F1)
     K = algebraic_closure(F1)
     z = zero(K)
@@ -170,7 +170,7 @@ end
     @test M^2 == M * M
   end
 
-  @testset "Singular ring for $F1" for F1 in [GF(3, 1), Nemo._GF(3, 1)]
+  @testset "Singular ring for $F1" for F1 in [GF(3, 1; cache=false), Nemo._GF(3, 1; cache=false)]
     p = characteristic(F1)
     K = algebraic_closure(F1)
     L = Oscar.singular_coeff_ring(K)