all: support map[f32]string and map[f64]string (float map keys) too (#8556)

vlib/builtin/map_of_floats_test.v

@@ -0,0 +1,27 @@
+fn test_map_of_f32() {
+	mut m32 := map[f32]string{}
+	m32[1.0] = 'one'
+	println(m32)
+	assert '$m32' == r"{1.: 'one'}"
+	for k, v in m32 {
+		assert typeof(k).name == 'f32'
+		assert typeof(v).name == 'string'
+		assert k == 1.0
+		assert v == 'one'
+	}
+}
+
+fn test_map_of_f64() {
+	mut m64 := {
+		3.14: 'pi'
+	}
+	m64[1.0] = 'one'
+	println(m64)
+	assert '$m64' == r"{3.14: 'pi', 1.: 'one'}"
+	for k, v in m64 {
+		assert typeof(k).name == 'f64'
+		assert typeof(v).name == 'string'
+		assert k in [1.0, 3.14]
+		assert v in ['pi', 'one']
+	}
+}