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/curlcheck.h

@@ -92,19 +92,27 @@
   } while(0)
 
 
-#define UNITTEST_START                          \
-  CURLcode test(char *arg)                      \
-  {                                             \
-    (void)arg;                                  \
-    if(unit_setup()) {                          \
-      fail("unit_setup() FAILURE");             \
-    }                                           \
-    else {
+#define UNITTEST_BEGIN_SIMPLE                   \
+  (void)arg;                                    \
+  {
 
-#define UNITTEST_STOP                           \
+#define UNITTEST_END_SIMPLE                     \
     goto unit_test_abort; /* avoid warning */   \
-unit_test_abort:                                \
-    unit_stop();                                \
   }                                             \
-  return (CURLcode)unitfail;                    \
-  }
+unit_test_abort:                                \
+  return (CURLcode)unitfail;
+
+#define UNITTEST_BEGIN(setupfunc)               \
+  (void)arg;                                    \
+  if(setupfunc) {                               \
+    fail("unit_setup() FAILURE");               \
+    return (CURLcode)unitfail;                  \
+  }                                             \
+  {
+
+#define UNITTEST_END(stopfunc)                  \
+    goto unit_test_abort; /* avoid warning */   \
+  }                                             \
+unit_test_abort:                                \
+  stopfunc;                                     \
+  return (CURLcode)unitfail;