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/configure.rs

@@ -449,7 +449,7 @@ async fn get_autoconfig(
 ) -> Option<Vec<ServerParams>> {
     if let Ok(res) = moz_autoconfigure(
         ctx,
-        format!(
+        &format!(
             "https://autoconfig.{}/mail/config-v1.1.xml?emailaddress={}",
             param_domain, param_addr_urlencoded
         ),
@@ -464,7 +464,7 @@ async fn get_autoconfig(
     if let Ok(res) = moz_autoconfigure(
         ctx,
         // the doc does not mention `emailaddress=`, however, Thunderbird adds it, see https://releases.mozilla.org/pub/thunderbird/ ,  which makes some sense
-        format!(
+        &format!(
             "https://{}/.well-known/autoconfig/mail/config-v1.1.xml?emailaddress={}",
             &param_domain, &param_addr_urlencoded
         ),
@@ -503,7 +503,7 @@ async fn get_autoconfig(
     // always SSL for Thunderbird's database
     if let Ok(res) = moz_autoconfigure(
         ctx,
-        format!("https://autoconfig.thunderbird.net/v1.1/{}", &param_domain),
+        &format!("https://autoconfig.thunderbird.net/v1.1/{}", &param_domain),
         param,
     )
     .await