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/server/tftpd.c

@@ -50,7 +50,7 @@
  * SPDX-License-Identifier: BSD-4-Clause-UC
  */
 
-#include "server_setup.h"
+#include "curl_setup.h"
 
 #ifdef HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h>
@@ -86,8 +86,42 @@
 #include <curlx.h> /* from the private lib dir */
 #include "getpart.h"
 #include "util.h"
-#include "server_sockaddr.h"
-#include "tftp.h"
+
+/*****************************************************************************
+*  This is a rewrite/clone of the arpa/tftp.h file for systems without it.   *
+*****************************************************************************/
+#define SEGSIZE 512 /* data segment size */
+
+#if defined(__GNUC__) && ((__GNUC__ >= 3) || \
+  ((__GNUC__ == 2) && defined(__GNUC_MINOR__) && (__GNUC_MINOR__ >= 7)))
+#  define PACKED_STRUCT __attribute__((__packed__))
+#else
+#  define PACKED_STRUCT /* NOTHING */
+#endif
+
+/* Using a packed struct as binary in a program is begging for problems, but
+   the tftpd server was written like this so we have this struct here to make
+   things build. */
+
+struct tftphdr {
+  unsigned short th_opcode; /* packet type */
+  unsigned short th_block;  /* all sorts of things */
+  char th_data[1];          /* data or error string */
+} PACKED_STRUCT;
+
+#define th_stuff th_block
+#define th_code  th_block
+#define th_msg   th_data
+
+#define TFTP_EUNDEF    0
+#define TFTP_ENOTFOUND 1
+#define TFTP_EACCESS   2
+#define TFTP_ENOSPACE  3
+#define TFTP_EBADOP    4
+#define TFTP_EBADID    5
+#define TFTP_EEXISTS   6
+#define TFTP_ENOUSER   7
+/****************************************************************************/
 
 /* include memdebug.h last */
 #include <memdebug.h>
@@ -528,7 +562,7 @@ static int synchnet(curl_socket_t f /* socket to flush */)
   return j;
 }
 
-int main(int argc, char **argv)
+static int test_tftpd(int argc, char **argv)
 {
   srvr_sockaddr_union_t me;
   struct tftphdr *tp;
@@ -826,7 +860,6 @@ int main(int argc, char **argv)
     }
 
     logmsg("end of one transfer");
-
   }
 
 tftpd_cleanup: