fix: do not save "Automatic" into configured_imap_certificate_checks

configured_imap_certificate_checks=0 means
accept invalid certificates unless provider database
says otherwise or SOCKS5 is enabled.
It should not be saved into the database anymore.

This bug was introduced in
<https://github.com/deltachat/deltachat-core-rust/pull/5854>
(commit 6b4532a08e)
and affects released core 1.142.4, 1.142.5 and 1.142.6.

Fix reverts faulty fix from
<https://github.com/deltachat/deltachat-core-rust/pull/5886>
(commit a268946f8d)
which changed the way configured_imap_certificate_checks=0
is interpreted and introduced problems
for existing setups with configured_imap_certificate_checks=0:
<https://github.com/deltachat/deltachat-core-rust/issues/5889>.

Existing test from previous fix is not reverted
and still applies.
Regression test is added to check that
configured_imap_certificate_checks
is not "0" for new accounts.

src/login_param.rs

@@ -265,7 +265,9 @@ impl LoginParam {
             | CertificateChecks::AcceptInvalidCertificates2 => Some(false),
         };
         let provider_strict_tls = self.provider.map(|provider| provider.opt.strict_tls);
-        user_strict_tls.or(provider_strict_tls).unwrap_or(true)
+        user_strict_tls
+            .or(provider_strict_tls)
+            .unwrap_or(self.socks5_config.is_some())
     }
 }