Improve Aliases test

Restricting to alias types in the source code stops the results from
changing when the standard library changes.

Using `pp()` instead of `getName` lets us see the results where the
underlying type doesn't have a name.

Author: owen-mc

go/ql/test/library-tests/semmle/go/Types/Aliases.expected

@@ -1,14 +1,4 @@
 | github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.FirstAlias | string | string |
+| github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.GenericSignatureAlias | github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.GenericSignature | func(T) T |
 | github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.SecondAlias | github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.FirstAlias | string |
-| internal/reflectlite.Kind | internal/abi.Kind | uint8 |
-| internal/reflectlite.nameOff | internal/abi.NameOff | int32 |
-| internal/reflectlite.textOff | internal/abi.TextOff | int32 |
-| internal/reflectlite.typeOff | internal/abi.TypeOff | int32 |
-| os.FileMode | io/fs.FileMode | uint32 |
-| os.syscallErrorType | syscall.Errno | uintptr |
-| reflect.aNameOff | internal/abi.NameOff | int32 |
-| reflect.aTextOff | internal/abi.TextOff | int32 |
-| reflect.aTypeOff | internal/abi.TypeOff | int32 |
-| runtime.nameOff | internal/abi.NameOff | int32 |
-| runtime.textOff | internal/abi.TextOff | int32 |
-| runtime.typeOff | internal/abi.TypeOff | int32 |
+| github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.TypeAlias | github.com/github/codeql-go/ql/test/library-tests/semmle/go/Types.GenericArray | [10]T |

go/ql/test/library-tests/semmle/go/Types/Aliases.ql

@@ -1,10 +1,10 @@
 import go
 
 string getQualifiedNameIfExists(Type t) {
-  if exists(t.getQualifiedName()) then result = t.getQualifiedName() else result = t.getName()
+  if exists(t.getQualifiedName()) then result = t.getQualifiedName() else result = t.pp()
 }
 
-from AliasType at
-where at.hasLocationInfo(_, _, _, _, _)
+from AliasType at, string filepath
+where at.hasLocationInfo(filepath, _, _, _, _) and filepath != ""
 select getQualifiedNameIfExists(at), getQualifiedNameIfExists(at.getRhs()),
   getQualifiedNameIfExists(at.getUnderlyingType())