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/unit1307.c

@@ -25,15 +25,6 @@
 
 #include "curl_fnmatch.h"
 
-static CURLcode unit_setup(void)
-{
-  return CURLE_OK;
-}
-
-static void unit_stop(void)
-{
-}
-
 #ifndef CURL_DISABLE_FTP
 
 /*
@@ -72,14 +63,10 @@ static const char *ret2name(int i)
   /* not reached */
 }
 
-enum system {
-  SYSTEM_CUSTOM,
-  SYSTEM_LINUX,
-  SYSTEM_MACOS
-};
-
-UNITTEST_START
+static CURLcode test_unit1307(char *arg)
 {
+  UNITTEST_BEGIN_SIMPLE
+
   struct testcase {
     const char *pattern;
     const char *string;
@@ -278,6 +265,13 @@ UNITTEST_START
   };
 
   int i;
+
+  enum system {
+    SYSTEM_CUSTOM,
+    SYSTEM_LINUX,
+    SYSTEM_MACOS
+  };
+
   enum system machine;
 
 #ifdef HAVE_FNMATCH
@@ -311,12 +305,16 @@ UNITTEST_START
       fail("pattern mismatch");
     }
   }
+
+  UNITTEST_END_SIMPLE
 }
-UNITTEST_STOP
 
 #else
 
-UNITTEST_START
-UNITTEST_STOP
+static CURLcode test_unit1307(char *arg)
+{
+  UNITTEST_BEGIN_SIMPLE
+  UNITTEST_END_SIMPLE
+}
 
 #endif