tests: drop mk-bundle exceptions

Using a mixture of techniques to avoid symbols collisions:
- reduce scope.
- add `t*_` / `T*_` prefix.
- move shared functions to `testutil.c`.
  (`suburl()`, `rlim2str()`)
- clone re-used lib*.c sources.
  (lib587, lib645)
- include shared symbols just once in re-used `lib*.c` sources.
  (using `LIB*_C` guards.)
- drop re-used `lib*.c` sources where they were identical or
  unused.
- make macros global.
- #undef macros before use.

What remain is the entry functions `test`, and `unit_setup`,
`unit_stop` in unit tests.

Also:
- fix formatting and other minor things along the way.
- add `const` where possible.
- sync some symbol names between tests.
- drop `mk-bundle-hints.sh` that's no longer necessary.

Closes #17468

tests/server/first.c

@@ -39,7 +39,7 @@ int main(int argc, char **argv)
   main_func = NULL;
   {
     size_t tmp;
-    for(tmp = 0; s_mains[tmp].ptr; ++tmp) {
+    for(tmp = 0; tmp < CURL_ARRAYSIZE(s_mains); ++tmp) {
       if(strcmp(main_name, s_mains[tmp].name) == 0) {
         main_func = s_mains[tmp].ptr;
         break;

tests/server/mk-bundle.pl

@@ -25,8 +25,6 @@
 
 # Bundle up individual tests into a single binary. The resulting binary can run
 # individual tests by passing their name (without '.c') as the first argument.
-#
-# Usage: mk-bundle.pl [<server_c>]
 
 use strict;
 use warnings;
@@ -82,8 +80,7 @@ foreach my $src (@src) {
 
 print <<FOOTER
 static const struct onemain s_mains[] = {
-${tlist}  {NULL, NULL}
-};
+$tlist};
 
 #include "first.c"
 FOOTER