refactor: rename _ex() -> _ext()

"ex" means "used to be, but no longer is".
"ext" means "extended", which is the intended meaning.
"Ext" is more common not only in the Rust ecosystem but in general.
We already had several people (myself included) asking
what "ex" is supposed to mean.

To reproduce this commit, search and replace `_ex(?!\w)` -> `_ext`.
But don't change `list_transports_ex` because it's public API.

src/sql.rs

@@ -451,7 +451,7 @@ impl Sql {
         G: Send + FnOnce(&mut rusqlite::Transaction<'_>) -> Result<H>,
     {
         let query_only = false;
-        self.transaction_ex(query_only, callback).await
+        self.transaction_ext(query_only, callback).await
     }
 
     /// Execute the function inside a transaction.
@@ -468,7 +468,7 @@ impl Sql {
     ///
     /// If the function returns an error, the transaction will be rolled back. If it does not return
     /// an error, the transaction will be committed.
-    pub async fn transaction_ex<G, H>(&self, query_only: bool, callback: G) -> Result<H>
+    pub async fn transaction_ext<G, H>(&self, query_only: bool, callback: G) -> Result<H>
     where
         H: Send + 'static,
         G: Send + FnOnce(&mut rusqlite::Transaction<'_>) -> Result<H>,