uefi-macros: Refactor GUID tests

Switch the tests from using `unsafe_guid!` to `guid!`. Both use the same
internal code, so we're testing more or less the same thing, but `guid!`
is a little more direct.

Also, as we previously did with the entry macro, split the GUID tests
into multiple files to make it easier to visually inspect the error
output.

The "good" test case has been removed since that's already covered in
plenty of places elsewhere.

Author: nicholasbishop

uefi-macros/tests/ui/guid.rs

@@ -0,0 +1,7 @@
+use uefi::Guid;
+use uefi_macros::guid;
+
+// Error span should point to the second group.
+const BadHexGroup2: Guid = guid!("aaaaaaaa-Gaaa-aaaa-aaaa-aaaaaaaaaaaa");
+
+fn main() {}

uefi-macros/tests/ui/guid.stderr

@@ -0,0 +1,5 @@
+error: GUID component "Gaaa" is not a hexadecimal number
+ --> tests/ui/guid_bad_hex_group2.rs:5:44
+  |
+5 | const BadHexGroup2: Guid = guid!("aaaaaaaa-Gaaa-aaaa-aaaa-aaaaaaaaaaaa");
+  |                                            ^^^^

uefi-macros/tests/ui/guid_bad_hex_group2.rs

@@ -0,0 +1,7 @@
+use uefi::Guid;
+use uefi_macros::guid;
+
+// Error span should point to the fifth group.
+const BadHexGroup5: Guid = guid!("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaG");
+
+fn main() {}

uefi-macros/tests/ui/guid_bad_hex_group2.stderr

@@ -0,0 +1,5 @@
+error: GUID component "aaaaaaaaaaaG" is not a hexadecimal number
+ --> tests/ui/guid_bad_hex_group5.rs:5:59
+  |
+5 | const BadHexGroup5: Guid = guid!("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaG");
+  |                                                           ^^^^^^^^^^^^

uefi-macros/tests/ui/guid_bad_hex_group5.rs

@@ -0,0 +1,7 @@
+use uefi::Guid;
+use uefi_macros::guid;
+
+// Fail because the length is wrong.
+const TooShort: Guid = guid!("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaa");
+
+fn main() {}

uefi-macros/tests/ui/guid_bad_hex_group5.stderr

@@ -0,0 +1,5 @@
+error: "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaa" is not a canonical GUID string (expected 36 bytes, found 35)
+ --> tests/ui/guid_bad_length.rs:5:30
+  |
+5 | const TooShort: Guid = guid!("aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaa");
+  |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^