chore: cleanup deprecated functions/defines (#7763)

this PR cleans up with some easy, deprecated stuff.

i roughly checked that they are no longer in use - by these checks,
other deprecated function were kept, eg.
dc_provider_new_from_email_with_dns() and dc_chat_is_protected() is
still used by deltatouch - to not add noise there, we remove them here
on the next cleanup ...

for DC_STR_*, however, if they are in used, the corresponding lines
should just be removed

this will cleanup https://c.delta.chat/deprecated.html as well

src/contact.rs

@@ -1299,18 +1299,6 @@ WHERE addr=?
         Ok(())
     }
 
-    /// Returns number of blocked contacts.
-    pub async fn get_blocked_cnt(context: &Context) -> Result<usize> {
-        let count = context
-            .sql
-            .count(
-                "SELECT COUNT(*) FROM contacts WHERE id>? AND blocked!=0",
-                (ContactId::LAST_SPECIAL,),
-            )
-            .await?;
-        Ok(count)
-    }
-
     /// Get blocked contacts.
     pub async fn get_all_blocked(context: &Context) -> Result<Vec<ContactId>> {
         Contact::update_blocked_mailinglist_contacts(context)