GHA: enable -Wunused-macros in clang-tidy jobs

Also fix fallouts found.

Windows clang-tidy CI job is a little pickier than I'd prefer due to the
`_CURL_TESTS_CONCAT=ON` option used there, and all macros considered
local, thus checked by the compiler. Upside: it revealed macro usage
dynamics in tests. If too annoying, `first.h` may be opted-out from the
concat logic. Some macros may also be deleted instead of `#if 0`-ing.

Follow-up to e0e56e9ae4 #21550
Follow-up to 5fa5cb3825 #20593

Closes #21554

tests/unit/unit1307.c

@@ -43,8 +43,10 @@
 
 #define MAC_DIFFER    0x40
 #define MAC_SHIFT     16
+#if 0
 #define MAC_MATCH     ((CURL_FNMATCH_MATCH   << MAC_SHIFT) | MAC_DIFFER)
 #define MAC_NOMATCH   ((CURL_FNMATCH_NOMATCH << MAC_SHIFT) | MAC_DIFFER)
+#endif
 #define MAC_FAIL      ((CURL_FNMATCH_FAIL    << MAC_SHIFT) | MAC_DIFFER)
 
 static const char *ret2name(int i)

tests/unit/unit1666.c

@@ -190,8 +190,6 @@ static CURLcode test_unit1666(const char *arg)
   UNITTEST_END_SIMPLE
 }
 
-#undef OID
-
 #else
 
 static CURLcode test_unit1666(const char *arg)

tests/unit/unit1667.c

@@ -37,9 +37,6 @@ struct test_1667 {
   CURLcode result_exp;
 };
 
-/* the size of the object needs to deduct the null terminator */
-#define OID(x) x, sizeof(x) - 1
-
 static bool test1667(const struct test_1667 *spec, size_t i,
                      struct dynbuf *dbuf)
 {
@@ -326,8 +323,6 @@ static CURLcode test_unit1667(const char *arg)
   UNITTEST_END_SIMPLE
 }
 
-#undef OID
-
 #else
 
 static CURLcode test_unit1667(const char *arg)