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

src/Makefile.am

@@ -67,6 +67,7 @@ if USE_UNICODE
 UNICODEFLAG = -municode
 endif
 
+# Get CURL_CFILES, CURLX_CFILES, CURL_HFILES variables
 include Makefile.inc
 
 curl_cfiles_gen =
@@ -80,7 +81,7 @@ else
 curl_CURLX = $(CURLX_CFILES)
 endif
 curltool_unity.c: $(top_srcdir)/scripts/mk-unity.pl $(CURL_CFILES) $(curl_cfiles_gen) $(curl_CURLX)
-	@PERL@ $(top_srcdir)/scripts/mk-unity.pl $(srcdir) $(CURL_CFILES) $(curl_cfiles_gen) $(curl_CURLX) > curltool_unity.c
+	@PERL@ $(top_srcdir)/scripts/mk-unity.pl --srcdir $(srcdir) --include $(CURL_CFILES) $(curl_cfiles_gen) $(curl_CURLX) > curltool_unity.c
 
 nodist_curl_SOURCES = curltool_unity.c
 curl_SOURCES =
@@ -112,7 +113,7 @@ libcurltool_la_CFLAGS =
 libcurltool_la_LDFLAGS = -static $(LINKFLAGS)
 if USE_UNITY
 libcurltool_unity.c: $(top_srcdir)/scripts/mk-unity.pl $(CURL_CFILES) $(curl_CURLX)
-	@PERL@ $(top_srcdir)/scripts/mk-unity.pl $(srcdir) $(CURL_CFILES) $(curl_CURLX) > libcurltool_unity.c
+	@PERL@ $(top_srcdir)/scripts/mk-unity.pl --srcdir $(srcdir) --include $(CURL_CFILES) $(curl_CURLX) > libcurltool_unity.c
 
 nodist_libcurltool_la_SOURCES = libcurltool_unity.c
 libcurltool_la_SOURCES =