Add path probing for modern RHEL-based systems.

On these systems `/etc/pki/tls/certs/ca-bundle.crt` is provided as a
legacy mechanism and isn't updated with system-wide installed roots
by default. This behavior can be changed by running `update-ca-trust
enable` but it would be better to just use the correct path. See
https://www.unix.com/man-page/centos/8/update-ca-trust/ for details.

Note that the legacy path still exists, so the new path needs to
come before it in the search order.

src/lib.rs

@@ -22,6 +22,7 @@ pub fn find_certs_dirs() -> Vec<PathBuf> {
         "/usr/lib/ssl",
         "/usr/ssl",
         "/etc/openssl",
+        "/etc/pki/ca-trust/extracted/pem",
         "/etc/pki/tls",
         "/etc/ssl",
         "/data/data/com.termux/files/usr/etc/tls",
@@ -66,6 +67,7 @@ pub fn probe() -> ProbeResult {
             "certs/ca-root-nss.crt",
             "certs/ca-bundle.crt",
             "CARootCertificates.pem",
+            "tls-ca-bundle.pem",
         ].iter() {
             try(&mut result.cert_file, certs_dir.join(cert));
         }