Fix multiple issues pointed out by the new compiler

kernel/src/process/credentials/credentials_.rs

@@ -34,8 +34,8 @@ pub(super) struct Credentials_ {
     supplementary_gids: RwLock<BTreeSet<Gid>>,
 
     /// The Linux capabilities.
+    ///
     /// This is not the capability (in static_cap.rs) enforced on rust objects.
-
     /// Capability that child processes can inherit
     inheritable_capset: AtomicCapSet,
 

kernel/src/process/posix_thread/robust_list.rs

@@ -84,7 +84,7 @@ impl<'a> FutexIter<'a> {
 
 const ROBUST_LIST_LIMIT: isize = 2048;
 
-impl<'a> Iterator for FutexIter<'a> {
+impl Iterator for FutexIter<'_> {
     type Item = Vaddr;
 
     fn next(&mut self) -> Option<Self::Item> {

kernel/src/process/process/process_group.rs

@@ -108,7 +108,7 @@ pub struct ProcessGroupGuard<'a> {
     inner: MutexGuard<'a, Inner>,
 }
 
-impl<'a> ProcessGroupGuard<'a> {
+impl ProcessGroupGuard<'_> {
     /// Returns an iterator over the processes in the group.
     pub fn iter(&self) -> ProcessGroupIter {
         ProcessGroupIter {

kernel/src/process/process_table.rs

@@ -44,7 +44,7 @@ pub struct ProcessTable<'a> {
     inner: MutexGuard<'a, BTreeMap<Pid, Arc<Process>>>,
 }
 
-impl<'a> ProcessTable<'a> {
+impl ProcessTable<'_> {
     /// Returns an iterator over the processes in the table.
     pub fn iter(&self) -> ProcessTableIter {
         ProcessTableIter {

kernel/src/process/process_vm/init_stack/aux_vec.rs

@@ -14,7 +14,6 @@ use crate::prelude::*;
 ///  > about the environment in which it is operating. The form of this information
 ///  > is a table of key-value pairs, where the keys are from the set of ‘AT_’
 ///  > values in elf.h.
-
 #[allow(non_camel_case_types)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 #[repr(u8)]

kernel/src/process/program_loader/elf/load_elf.rs

@@ -338,11 +338,7 @@ fn map_segment_vmo(
     vm_map_options = vm_map_options.offset(offset).handle_page_faults_around();
     let map_addr = vm_map_options.build()?;
 
-    let anonymous_map_size: usize = if total_map_size > segment_size {
-        total_map_size - segment_size
-    } else {
-        0
-    };
+    let anonymous_map_size: usize = total_map_size.saturating_sub(segment_size);
 
     if anonymous_map_size > 0 {
         let mut anonymous_map_options = root_vmar