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>

tpm/src/emulator.rs

@@ -3,17 +3,19 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
-use crate::socket::SocketDev;
-use crate::{Commands, MemberType, Ptm, PtmCap, PtmEst, PtmInit, PtmResult, PtmSetBufferSize};
-use crate::{TPM_CRB_BUFFER_MAX, TPM_SUCCESS};
-use anyhow::anyhow;
-use libc::c_void;
-use libc::{sockaddr_storage, socklen_t};
 use std::os::unix::io::RawFd;
 use std::path::Path;
 use std::{mem, ptr};
+
+use anyhow::anyhow;
+use libc::c_void;
+use libc::{sockaddr_storage, socklen_t};
 use thiserror::Error;
 
+use crate::socket::SocketDev;
+use crate::{Commands, MemberType, Ptm, PtmCap, PtmEst, PtmInit, PtmResult, PtmSetBufferSize};
+use crate::{TPM_CRB_BUFFER_MAX, TPM_SUCCESS};
+
 const TPM_REQ_HDR_SIZE: usize = 10;
 
 /* capability flags returned by PTM_GET_CAPABILITY */

tpm/src/socket.rs

@@ -3,10 +3,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
-use anyhow::anyhow;
 use std::io::Read;
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::os::unix::net::UnixStream;
+
+use anyhow::anyhow;
 use thiserror::Error;
 use vmm_sys_util::sock_ctrl_msg::ScmSocket;