tests: always make bundles, adapt build and tests

Make test bundles the default. Drop non-bundle build mode.
Also do all the optimizations and tidy-ups this allows, simpler builds,
less bundle exceptions, streamlined build mechanics.

Also rework the init/deinit macro magic for unit tests. The new method
allows using unique init/deinit function names, and calling them with
arguments. This is in turn makes it possible to reduce the use of global
variables.

Note this drop existing build options `-DCURL_TEST_BUNDLES=` from cmake
and `--enable-test-bundles` / `--disable-test-bundles` from autotools.

Also:
- rename test entry functions to have unique names: `test_<testname>`
  This removes the last exception that was handled in the generator.
- fix `make dist` to not miss test sources with test bundles enabled.
- sync and merge `tests/mk-bundle.pl` into `scripts/mk-unity.pl`.
- mk-unity.pl: add `--embed` option and use it when `CURL_CLANG_TIDY=ON`
  to ensure that `clang-tidy` does not miss external test C sources.
  (because `clang-tidy` ignores code that's #included.)
- tests/unit: drop no-op setup/stop functions.
- tests: reduce symbol scopes, global macros, other fixes and tidy-ups.
- tool1621: fix to run, also fix it to pass.
- sockfilt: fix Windows compiler warning in certain unity include order,
  by explicitly including `warnless.h`.

Follow-up to 6897aeb105 #17468

Closes #17590

tests/unit/unit2604.c

@@ -25,27 +25,20 @@
 #include "vssh/curl_path.h"
 #include "memdebug.h"
 
-static CURLcode unit_setup(void)
+static CURLcode test_unit2604(char *arg)
 {
-  return CURLE_OK;
-}
+  UNITTEST_BEGIN_SIMPLE
 
-static void unit_stop(void)
-{
-}
-
-
-struct set {
-  const char *cp;
-  const char *expect; /* the returned content */
-  const char *next;   /* what cp points to after the call */
-  const char *home;
-  CURLcode result;
-};
-
-UNITTEST_START
 #ifdef USE_SSH
-{
+
+  struct set {
+    const char *cp;
+    const char *expect; /* the returned content */
+    const char *next;   /* what cp points to after the call */
+    const char *home;
+    CURLcode result;
+  };
+
 #if defined(CURL_GNUC_DIAG) || defined(__clang__)
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Woverlength-strings"
@@ -79,7 +72,7 @@ UNITTEST_START
   };
 
 #if defined(CURL_GNUC_DIAG) || defined(__clang__)
-#pragma GCC diagnostic warning "-Woverlength-strings"
+#pragma GCC diagnostic pop
 #endif
 
   list[0].cp = calloc(1, too_long + 1);
@@ -113,11 +106,8 @@ UNITTEST_START
   }
 
   free(CURL_UNCONST(list[0].cp));
+
+#endif
+
+  UNITTEST_END_SIMPLE
 }
-#if defined(CURL_GNUC_DIAG) || defined(__clang__)
-#pragma GCC diagnostic pop
-#endif
-
-#endif
-
-UNITTEST_STOP