misc: Adapt consistent import style formatting

Historically the Cloud Hypervisor coding style has been to ensure that
all imports are ordered and placed in a single group. Unfortunately
cargo fmt has no support for ensuring that all imports are in a single
group so if whitespace lines were added as part of the import statements
then they would only be odered correctly in the group.

By adopting "group_imports="StdExternalCrate" we can enforce a style
where imports are placed in at most three groups for std, external
crates and the crate itself. Choosing a style enforceable by the tooling
reduces the reviewer burden.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

vmm/src/igvm/igvm_loader.rs

@@ -2,18 +2,6 @@
 //
 // Copyright © 2023, Microsoft Corporation
 //
-use crate::cpu::CpuManager;
-use zerocopy::AsBytes;
-
-use crate::igvm::{
-    loader::Loader, BootPageAcceptance, IgvmLoadedInfo, StartupMemoryType, HV_PAGE_SIZE,
-};
-use crate::memory_manager::MemoryManager;
-use igvm::{snp_defs::SevVmsa, IgvmDirectiveHeader, IgvmFile, IgvmPlatformHeader, IsolationType};
-use igvm_defs::{
-    IgvmPageDataType, IgvmPlatformType, IGVM_VHS_PARAMETER, IGVM_VHS_PARAMETER_INSERT,
-};
-use mshv_bindings::*;
 use std::collections::HashMap;
 use std::ffi::CString;
 use std::io::Read;
@@ -21,12 +9,24 @@ use std::io::Seek;
 use std::io::SeekFrom;
 use std::mem::size_of;
 use std::sync::{Arc, Mutex};
-use thiserror::Error;
 
-#[cfg(feature = "sev_snp")]
-use crate::GuestMemoryMmap;
+use igvm::{snp_defs::SevVmsa, IgvmDirectiveHeader, IgvmFile, IgvmPlatformHeader, IsolationType};
+use igvm_defs::{
+    IgvmPageDataType, IgvmPlatformType, IGVM_VHS_PARAMETER, IGVM_VHS_PARAMETER_INSERT,
+};
 #[cfg(feature = "sev_snp")]
 use igvm_defs::{MemoryMapEntryType, IGVM_VHS_MEMORY_MAP_ENTRY};
+use mshv_bindings::*;
+use thiserror::Error;
+use zerocopy::AsBytes;
+
+use crate::cpu::CpuManager;
+use crate::igvm::{
+    loader::Loader, BootPageAcceptance, IgvmLoadedInfo, StartupMemoryType, HV_PAGE_SIZE,
+};
+use crate::memory_manager::MemoryManager;
+#[cfg(feature = "sev_snp")]
+use crate::GuestMemoryMmap;
 
 #[derive(Debug, Error)]
 pub enum Error {

vmm/src/igvm/loader.rs

@@ -2,7 +2,6 @@
 //
 // Copyright © 2023, Microsoft Corporation
 //
-use crate::igvm::{BootPageAcceptance, StartupMemoryType, HV_PAGE_SIZE};
 use range_map_vec::{Entry, RangeMap};
 use thiserror::Error;
 use vm_memory::bitmap::AtomicBitmap;
@@ -11,6 +10,8 @@ use vm_memory::{
     GuestMemoryRegion,
 };
 
+use crate::igvm::{BootPageAcceptance, StartupMemoryType, HV_PAGE_SIZE};
+
 /// Structure to hold the guest memory info/layout to check
 /// the if the memory is accepted within the layout.
 /// Adds up the total bytes written to the guest memory