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/unit1300.c

@@ -25,10 +25,6 @@
 
 #include "llist.h"
 
-static struct Curl_llist llist;
-
-static struct Curl_llist llist_destination;
-
 static void test_Curl_llist_dtor(void *key, void *value)
 {
   /* used by the llist API, does nothing here */
@@ -36,19 +32,13 @@ static void test_Curl_llist_dtor(void *key, void *value)
   (void)value;
 }
 
-static CURLcode unit_setup(void)
+static CURLcode test_unit1300(char *arg)
 {
-  Curl_llist_init(&llist, test_Curl_llist_dtor);
-  Curl_llist_init(&llist_destination, test_Curl_llist_dtor);
-  return CURLE_OK;
-}
+  UNITTEST_BEGIN_SIMPLE
 
-static void unit_stop(void)
-{
-}
+  struct Curl_llist llist;
+  struct Curl_llist llist_destination;
 
-UNITTEST_START
-{
   int unusedData_case1 = 1;
   int unusedData_case2 = 2;
   int unusedData_case3 = 3;
@@ -62,6 +52,9 @@ UNITTEST_START
   struct Curl_llist_node *to_remove;
   size_t llist_size;
 
+  Curl_llist_init(&llist, test_Curl_llist_dtor);
+  Curl_llist_init(&llist_destination, test_Curl_llist_dtor);
+
   /**
    * testing llist_init
    * case 1:
@@ -271,5 +264,6 @@ UNITTEST_START
 
   Curl_llist_destroy(&llist, NULL);
   Curl_llist_destroy(&llist_destination, NULL);
+
+  UNITTEST_END_SIMPLE
 }
-UNITTEST_STOP