chore(offchain): suppress rust-clippy warnings

Full list of warnings:
- avoid warning `large_enum_variant` from cargo clippy on `pub enum MachineOneof`, built from grpc-interfaces. More at https://rust-lang.github.io/rust-clippy/master/index.html#large_enum_variant
- allow enum variants with same suffix. More at https://rust-lang.github.io/rust-clippy/master/index.html#enum_variant_names.
- allow too many arguments in fn. More at https://rust-lang.github.io/rust-clippy/master/index.html#/too_many_arguments.
- allow capitalized acronym. More at https://rust-lang.github.io/rust-clippy/master/index.html#upper_case_acronyms.

offchain/advance-runner/src/server_manager/error.rs

@@ -5,6 +5,7 @@ use snafu::Snafu;
 
 #[derive(Debug, Snafu)]
 #[snafu(visibility(pub(super)))]
+#[allow(clippy::enum_variant_names)]
 pub enum ServerManagerError {
     #[snafu(display("failed to connect to server-manager"))]
     ConnectionError { source: tonic::transport::Error },

offchain/advance-runner/src/snapshot/fs_manager.rs

@@ -10,6 +10,7 @@ use super::config::FSManagerConfig;
 use super::{Snapshot, SnapshotManager};
 
 #[derive(Debug, Snafu)]
+#[allow(clippy::enum_variant_names)]
 pub enum FSSnapshotError {
     #[snafu(display("failed to follow latest symlink"))]
     ReadLinkError { source: std::io::Error },

offchain/clippy.toml

@@ -0,0 +1,2 @@
+# This avoids warning `large_enum_variant` on `pub enum MachineOneof`, built from grpc-interfaces.
+enum-variant-size-threshold = 2500

offchain/dispatcher/src/auth.rs

@@ -58,6 +58,7 @@ pub struct AuthEnvCLIConfig {
 }
 
 #[derive(Debug, Clone)]
+#[allow(clippy::upper_case_acronyms)]
 pub enum AuthConfig {
     Mnemonic {
         mnemonic: String,

offchain/dispatcher/src/dispatcher.rs

@@ -121,6 +121,7 @@ pub async fn start(
 }
 
 #[instrument(level = "trace", skip_all)]
+#[allow(clippy::too_many_arguments)]
 async fn process_block(
     block: &Block,
 

offchain/state-server/src/error.rs

@@ -9,6 +9,7 @@ use url::ParseError;
 
 #[derive(Debug, Snafu)]
 #[snafu(visibility(pub(crate)))]
+#[allow(clippy::enum_variant_names)]
 pub enum StateServerError {
     #[snafu(display("tonic error"))]
     TonicError { source: TonicError },