float: make default string representations for floats become alike

vlib/v/tests/num_lit_call_method_test.v

@@ -21,8 +21,17 @@ fn test_float_lit_call_method() {
 	x4 := .003e2.str()
 	assert x4 == '0.3'
 	x5 := 2.e-3.str()
-	assert x5 == '2.e-03'
+	assert x5 == '0.002'
 	x6 := 5.0.str()
 	assert x6 == '5.'
 	// x7 := 5..str()    Syntax `5.` is allowed, but do not call method on it (`5..str()` is parsed as a range). Use `5.0.str()` instead.
+	x8 := 7.345e-7.str()
+	assert x8 == '7.345e-07'
+	x9 := 5.725e6.str()
+	assert x9 == '5.725e+06'
+
+	a := f32(12.3).str()
+	assert a[0..4] == '12.3' // there is still trailing garbage
+	assert f32(7.345e-7).str() == '7.345e-07'
+	assert f32(5.725e6).str() == '5.725e+06'
 }