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/unit1606.c

@@ -26,28 +26,27 @@
 #include "speedcheck.h"
 #include "urldata.h"
 
-static struct Curl_easy *t1606_easy;
-
-static CURLcode unit_setup(void)
+static CURLcode t1606_setup(struct Curl_easy **easy)
 {
   CURLcode res = CURLE_OK;
 
   global_init(CURL_GLOBAL_ALL);
-  t1606_easy = curl_easy_init();
-  if(!t1606_easy) {
+  *easy = curl_easy_init();
+  if(!*easy) {
     curl_global_cleanup();
     return CURLE_OUT_OF_MEMORY;
   }
   return res;
 }
 
-static void unit_stop(void)
+static void t1606_stop(struct Curl_easy *easy)
 {
-  curl_easy_cleanup(t1606_easy);
+  curl_easy_cleanup(easy);
   curl_global_cleanup();
 }
 
-static int runawhile(long time_limit,
+static int runawhile(struct Curl_easy *easy,
+                     long time_limit,
                      long speed_limit,
                      curl_off_t speed,
                      int dec)
@@ -57,14 +56,14 @@ static int runawhile(long time_limit,
   CURLcode result;
   int finaltime;
 
-  curl_easy_setopt(t1606_easy, CURLOPT_LOW_SPEED_LIMIT, speed_limit);
-  curl_easy_setopt(t1606_easy, CURLOPT_LOW_SPEED_TIME, time_limit);
-  Curl_speedinit(t1606_easy);
+  curl_easy_setopt(easy, CURLOPT_LOW_SPEED_LIMIT, speed_limit);
+  curl_easy_setopt(easy, CURLOPT_LOW_SPEED_TIME, time_limit);
+  Curl_speedinit(easy);
 
   do {
     /* fake the current transfer speed */
-    t1606_easy->progress.current_speed = speed;
-    result = Curl_speedcheck(t1606_easy, now);
+    easy->progress.current_speed = speed;
+    result = Curl_speedcheck(easy, now);
     if(result)
       break;
     /* step the time */
@@ -77,17 +76,24 @@ static int runawhile(long time_limit,
   return finaltime;
 }
 
-UNITTEST_START
-  fail_unless(runawhile(41, 41, 40, 0) == 41,
+static CURLcode test_unit1606(char *arg)
+{
+  struct Curl_easy *easy;
+
+  UNITTEST_BEGIN(t1606_setup(&easy))
+
+  fail_unless(runawhile(easy, 41, 41, 40, 0) == 41,
               "wrong low speed timeout");
-  fail_unless(runawhile(21, 21, 20, 0) == 21,
+  fail_unless(runawhile(easy, 21, 21, 20, 0) == 21,
               "wrong low speed timeout");
-  fail_unless(runawhile(60, 60, 40, 0) == 60,
+  fail_unless(runawhile(easy, 60, 60, 40, 0) == 60,
               "wrong log speed timeout");
-  fail_unless(runawhile(50, 50, 40, 0) == 50,
+  fail_unless(runawhile(easy, 50, 50, 40, 0) == 50,
               "wrong log speed timeout");
-  fail_unless(runawhile(40, 40, 40, 0) == 99,
+  fail_unless(runawhile(easy, 40, 40, 40, 0) == 99,
               "should not time out");
-  fail_unless(runawhile(10, 50, 100, 2) == 36,
+  fail_unless(runawhile(easy, 10, 50, 100, 2) == 36,
               "bad timeout");
-UNITTEST_STOP
+
+  UNITTEST_END(t1606_stop(easy))
+}