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/unit1395.c

@@ -28,25 +28,18 @@ extern int dedotdotify(const char *input, size_t clen, char **out);
 
 #include "memdebug.h"
 
-static CURLcode unit_setup(void)
+static CURLcode test_unit1395(char *arg)
 {
-  return CURLE_OK;
-}
-
-static void unit_stop(void)
-{
-
-}
-
-struct dotdot {
-  const char *input;
-  const char *output;
-};
-
-UNITTEST_START
+  UNITTEST_BEGIN_SIMPLE
 
   unsigned int i;
   int fails = 0;
+
+  struct dotdot {
+    const char *input;
+    const char *output;
+  };
+
   const struct dotdot pairs[] = {
     { "%2f%2e%2e%2f/../a", "%2f%2e%2e%2f/a" },
     { "%2f%2e%2e%2f/../", "%2f%2e%2e%2f/" },
@@ -148,4 +141,5 @@ UNITTEST_START
 
   fail_if(fails, "output mismatched");
 
-UNITTEST_STOP
+  UNITTEST_END_SIMPLE
+}