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/unit1609.c

@@ -29,17 +29,10 @@
 
 #include "memdebug.h" /* LAST include file */
 
-static void unit_stop(void)
-{
-  curl_global_cleanup();
-}
-
-static CURLcode unit_setup(void)
+static CURLcode t1609_setup(void)
 {
   CURLcode res = CURLE_OK;
-
   global_init(CURL_GLOBAL_ALL);
-
   return res;
 }
 
@@ -75,8 +68,10 @@ Test:
  expected result: cached address has zero timestamp and new address
 */
 
-UNITTEST_START
+static CURLcode test_unit1609(char *arg)
 {
+  UNITTEST_BEGIN(t1609_setup())
+
   struct testcase {
     /* host:port:address[,address]... */
     const char *optval;
@@ -217,5 +212,6 @@ error:
   curl_easy_cleanup(easy);
   curl_multi_cleanup(multi);
   curl_slist_free_all(list);
+
+  UNITTEST_END(curl_global_cleanup())
 }
-UNITTEST_STOP