Debloat the binary by using less AsRef arguments

Using `impl AsRef<str>` as the argument instead of `&str` makes it
possible to call the function with `&str`, `String` and other types
that implement `AsRef` trait.

The cost of it is that compiled binary contains mulitple versions of
the same function, one for each variant of types. If function contains
multiple generic `impl AsRef` arguments, the number of versions possibly
compiled into binary grows exponentially with the number of arguments.

Simple way to avoid it is to call `.as_ref()` on the caller side to
convert the argument to `&str`. In most cases even adding a `&` and
relying on `Deref` coercion is sufficient.

This patch changes many functions that accepted `impl AsRef<str>` and
`impl AsRef<Path>` to accept `&str` and `&Path` instead.

In some places `.clone()` calls are removed. Calling `.clone()` on
`String` and passing `String` to a function accepting `impl
AsRef<str>` is completely unnecessary as `&str` reference could be
passed instead. There is no clippy warning against it yet, but
changing argument type to `&str` allowed to find these cases.

The result of debloating is not impressive, several hundred kilobytes
are saved, which is about 3% of the `.so` binary, but the code is
cleaner too.

src/stock_str.rs

@@ -925,7 +925,7 @@ impl Context {
         chat::add_device_msg(self, Some("core-about-device-chat"), Some(&mut msg)).await?;
 
         let image = include_bytes!("../assets/welcome-image.jpg");
-        let blob = BlobObject::create(self, "welcome-image.jpg".to_string(), image).await?;
+        let blob = BlobObject::create(self, "welcome-image.jpg", image).await?;
         let mut msg = Message::new(Viewtype::Image);
         msg.param.set(Param::File, blob.as_name());
         chat::add_device_msg(self, Some("core-welcome-image"), Some(&mut msg)).await?;