typo fixes all over the place

found and semi-manually replaced by using:
 codespell -L mut -L crate -i 3 -w

Mostly in comments, but also email notification and two occurrences
of misspelled  'reserved' struct member, which where not used and
cargo build did not complain about the change, soo ...

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/tape/media_pool.rs

@@ -3,7 +3,7 @@
 //! A set of backup medias.
 //!
 //! This struct manages backup media state during backup. The main
-//! purpose is to allocate media sets and assing new tapes to it.
+//! purpose is to allocate media sets and assign new tapes to it.
 //!
 //!
 
@@ -137,7 +137,7 @@ impl MediaPool {
         &self.name
     }
 
-    /// Retruns encryption settings
+    /// Returns encryption settings
     pub fn encrypt_fingerprint(&self) -> Option<Fingerprint> {
         self.encrypt_fingerprint.clone()
     }
@@ -286,7 +286,7 @@ impl MediaPool {
         Ok(list)
     }
 
-    // tests if the media data is considered as expired at sepcified time
+    // tests if the media data is considered as expired at specified time
     pub fn media_is_expired(&self, media: &BackupMedia, current_time: i64) -> bool {
         if media.status() != &MediaStatus::Full {
             return false;