curl: support embedding a CA bundle

Add the ability to embed a CA bundle into the curl binary. It is used
when no other runtime or build-time option set one.

This helps curl-for-win macOS and Linux builds to run standalone, and
also helps Windows builds to avoid picking up the CA bundle from an
arbitrary (possibly world-writable) location (though this behaviour is
not currently disablable).

Usage:
- cmake: `-DCURL_CA_EMBED=/path/to/curl-ca-bundle.crt`
- autotools: `--with-ca-embed=/path/to/curl-ca-bundle.crt`
- Makefile.mk: `CURL_CA_EMBED=/path/to/curl-ca-bundle.crt`

Also add new command-line option `--dump-ca-embed` to dump the embedded
CA bundle to standard output.

Closes #14059

src/tool_getparam.h

@@ -35,6 +35,7 @@ typedef enum {
   PARAM_MANUAL_REQUESTED,
   PARAM_VERSION_INFO_REQUESTED,
   PARAM_ENGINES_REQUESTED,
+  PARAM_CA_EMBED_REQUESTED,
   PARAM_GOT_EXTRA_PARAMETER,
   PARAM_BAD_NUMERIC,
   PARAM_NEGATIVE_NUMERIC,