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/tunit/Makefile.am

@@ -41,7 +41,10 @@ AM_CPPFLAGS = -I$(top_srcdir)/include        \
               -I$(top_srcdir)/tests/unit     \
               -I$(top_srcdir)/tests/tunit
 
-EXTRA_DIST = CMakeLists.txt README.md
+# Get BUNDLE, BUNDLE_SRC, FIRSTFILES, UTILS, TESTFILES variables
+include Makefile.inc
+
+EXTRA_DIST = CMakeLists.txt README.md $(UTILS) $(TESTFILES)
 
 CFLAGS += @CURL_CFLAG_EXTRAS@
 
@@ -49,7 +52,7 @@ CFLAGS += @CURL_CFLAG_EXTRAS@
 LIBS = $(BLANK_AT_MAKETIME)
 
 LDADD = $(top_builddir)/src/libcurltool.la   \
-        $(top_builddir)/lib/libcurl.la      \
+        $(top_builddir)/lib/libcurl.la       \
         @LIBCURL_PC_LDFLAGS_PRIVATE@ @LIBCURL_PC_LIBS_PRIVATE@
 
 AM_CPPFLAGS += -DCURL_STATICLIB -DUNITTESTS
@@ -60,21 +63,15 @@ if CURLDEBUG
 AM_CPPFLAGS += -DCURLDEBUG
 endif
 
-BUNDLE=tunits
+AM_CPPFLAGS += -DCURL_NO_OLDIES -DCURL_DISABLE_DEPRECATION
 
 if BUILD_UNITTESTS
-if USE_TEST_BUNDLES
-tool_bundle.c: $(top_srcdir)/tests/mk-bundle.pl Makefile.inc
-	@PERL@ $(top_srcdir)/tests/mk-bundle.pl $(srcdir) > tool_bundle.c
+$(BUNDLE_SRC): $(top_srcdir)/scripts/mk-unity.pl Makefile.inc $(FIRSTFILES) $(UTILS) $(TESTFILES)
+	@PERL@ $(top_srcdir)/scripts/mk-unity.pl --include $(UTILS) --test $(TESTFILES) > $(BUNDLE_SRC)
 
 noinst_PROGRAMS = $(BUNDLE)
-nodist_tunits_SOURCES = tool_bundle.c
-CLEANFILES = tool_bundle.c
-else
-# Makefile.inc provides neat definitions
-include Makefile.inc
-noinst_PROGRAMS = $(TOOLPROGS)
-endif
+nodist_tunits_SOURCES = $(BUNDLE_SRC)
+CLEANFILES = $(BUNDLE_SRC)
 else
 noinst_PROGRAMS =
 endif
@@ -87,7 +84,7 @@ CS_ = $(CS_0)
 # ignore generated C files since they play by slightly different rules!
 checksrc:
 	$(CHECKSRC)(@PERL@ $(top_srcdir)/scripts/checksrc.pl -D$(srcdir) \
-	  -W$(srcdir)/tool_bundle.c \
+	  -W$(srcdir)/$(BUNDLE_SRC) \
 	  $(srcdir)/*.[ch])
 
 if NOT_CURL_CI