Makefile.dist: delete

It had shorthand aliases to launch `./configure` and
`./configure --with-openssl`. The former hasn't worked for a long while
because of missing TLS.

Its `ca-bundle` and `ca-firefox` targets have been broken for 2.5 years
till recently. These targets also exist in `./configure` and have been
working all along.

Also:
- cmake: add support `curl-ca-bundle` and `curl-ca-firefox` targets.
- tests/testcurl.pl: drop obsolete build logic.

Closes #16094

scripts/maketgz

@@ -68,10 +68,9 @@ fi
 
 #
 # As a precaution, remove all *.dist files that may be lying around, to reduce
-# the risk of old leftovers getting shipped. The root 'Makefile.dist' is the
-# exception.
+# the risk of old leftovers getting shipped.
 echo "removing all old *.dist files"
-find . -name "*.dist" -a ! -name Makefile.dist -exec rm {} \;
+find . -name "*.dist" -exec rm {} \;
 
 numeric="$(printf "%02x%02x%02x\n" "$major" "$minor" "$patch")"