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/unit1399.c

@@ -26,17 +26,6 @@
 #include "urldata.h"
 #include "progress.h"
 
-static int usec_magnitude = 1000000;
-
-static CURLcode unit_setup(void)
-{
-  return CURLE_OK;
-}
-
-static void unit_stop(void)
-{
-}
-
 /*
  * Invoke Curl_pgrsTime for TIMER_STARTSINGLE to trigger the behavior that
  * manages is_t_startransfer_set, but fake the t_startsingle time for purposes
@@ -53,6 +42,8 @@ static void fake_t_startsingle_time(struct Curl_easy *data,
 
 static bool usec_matches_seconds(timediff_t time_usec, int expected_seconds)
 {
+  static int usec_magnitude = 1000000;
+
   int time_sec = (int)(time_usec / usec_magnitude);
   bool same = (time_sec == expected_seconds);
   curl_mfprintf(stderr, "is %d us same as %d seconds? %s\n",
@@ -80,7 +71,10 @@ static void expect_timer_seconds(struct Curl_easy *data, int seconds)
  * E.g., if t_starttransfer took 2 seconds initially and took another 1
  * second for the redirect request, then the resulting t_starttransfer should
  * be 3 seconds. */
-UNITTEST_START
+static CURLcode test_unit1399(char *arg)
+{
+  UNITTEST_BEGIN_SIMPLE
+
   struct Curl_easy data;
   struct curltime now = curlx_now();
 
@@ -116,4 +110,6 @@ UNITTEST_START
   Curl_pgrsTime(&data, TIMER_STARTTRANSFER);
 
   expect_timer_seconds(&data, 3);
-UNITTEST_STOP
+
+  UNITTEST_END_SIMPLE
+}