Update to Rust 1.59 and 2021 edition (#3038)

## Proposed Changes

Lots of lint updates related to `flat_map`, `unwrap_or_else` and string patterns. I did a little more creative refactoring in the op pool, but otherwise followed Clippy's suggestions.

## Additional Info

We need this PR to unblock CI.

testing/ef_tests/Cargo.toml

@@ -2,7 +2,7 @@
 name = "ef_tests"
 version = "0.2.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
-edition = "2018"
+edition = "2021"
 
 [features]
 # `ef_tests` feature must be enabled to actually run the tests

testing/ef_tests/src/cases/epoch_processing.rs

@@ -259,10 +259,7 @@ impl<E: EthSpec, T: EpochTransition<E>> LoadCase for EpochProcessing<E, T> {
 
 impl<E: EthSpec, T: EpochTransition<E>> Case for EpochProcessing<E, T> {
     fn description(&self) -> String {
-        self.metadata
-            .description
-            .clone()
-            .unwrap_or_else(String::new)
+        self.metadata.description.clone().unwrap_or_default()
     }
 
     fn is_enabled_for_fork(fork_name: ForkName) -> bool {

testing/ef_tests/src/cases/operations.rs

@@ -304,10 +304,7 @@ impl<E: EthSpec, O: Operation<E>> LoadCase for Operations<E, O> {
 
 impl<E: EthSpec, O: Operation<E>> Case for Operations<E, O> {
     fn description(&self) -> String {
-        self.metadata
-            .description
-            .clone()
-            .unwrap_or_else(String::new)
+        self.metadata.description.clone().unwrap_or_default()
     }
 
     fn is_enabled_for_fork(fork_name: ForkName) -> bool {

testing/ef_tests/src/cases/rewards.rs

@@ -103,10 +103,7 @@ impl<E: EthSpec> LoadCase for RewardsTest<E> {
 
 impl<E: EthSpec> Case for RewardsTest<E> {
     fn description(&self) -> String {
-        self.metadata
-            .description
-            .clone()
-            .unwrap_or_else(String::new)
+        self.metadata.description.clone().unwrap_or_default()
     }
 
     fn result(&self, _case_index: usize, fork_name: ForkName) -> Result<(), Error> {

testing/ef_tests/src/cases/sanity_blocks.rs

@@ -56,10 +56,7 @@ impl<E: EthSpec> LoadCase for SanityBlocks<E> {
 
 impl<E: EthSpec> Case for SanityBlocks<E> {
     fn description(&self) -> String {
-        self.metadata
-            .description
-            .clone()
-            .unwrap_or_else(String::new)
+        self.metadata.description.clone().unwrap_or_default()
     }
 
     fn result(&self, _case_index: usize, fork_name: ForkName) -> Result<(), Error> {

testing/ef_tests/src/cases/sanity_slots.rs

@@ -50,10 +50,7 @@ impl<E: EthSpec> LoadCase for SanitySlots<E> {
 
 impl<E: EthSpec> Case for SanitySlots<E> {
     fn description(&self) -> String {
-        self.metadata
-            .description
-            .clone()
-            .unwrap_or_else(String::new)
+        self.metadata.description.clone().unwrap_or_default()
     }
 
     fn result(&self, _case_index: usize, fork_name: ForkName) -> Result<(), Error> {

testing/eth1_test_rig/Cargo.toml

@@ -2,7 +2,7 @@
 name = "eth1_test_rig"
 version = "0.2.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 tokio = { version = "1.14.0", features = ["time"] }

testing/node_test_rig/Cargo.toml

@@ -2,7 +2,7 @@
 name = "node_test_rig"
 version = "0.2.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 environment = { path = "../../lighthouse/environment" }

testing/simulator/Cargo.toml

@@ -2,7 +2,7 @@
 name = "simulator"
 version = "0.2.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
-edition = "2018"
+edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 

testing/state_transition_vectors/Cargo.toml

@@ -2,7 +2,7 @@
 name = "state_transition_vectors"
 version = "0.1.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
-edition = "2018"
+edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 

testing/test-test_logger/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "test-test_logger"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 

testing/web3signer_tests/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "web3signer_tests"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 build = "build.rs"