Get rid of spectral rust crate. (pantsbuild#18774)

This get rids of a bunch of packages we don't really need (num-*) and
one package
[rustc-serialize](https://github.com/rust-lang-deprecated/rustc-serialize)
which was deprecated

from what I can tell, this package was added ~4 years ago... my guess
back then, rust was missing some of the testing features that it
provided, I think this is no longer the case.

src/rust/engine/process_execution/Cargo.toml

@@ -57,7 +57,6 @@ maplit = "1.0.1"
 mock = { path = "../testutil/mock" }
 parking_lot = "0.12"
 sharded_lmdb = { path = "../sharded_lmdb" }
-spectral = "0.6.0"
 tempfile = "3"
 testutil = { path = "../testutil" }
 tokio = { version = "1.21", features = ["macros"] }

src/rust/engine/process_execution/docker/Cargo.toml

@@ -35,7 +35,6 @@ maplit = "1.0.1"
 mock = { path = "../../testutil/mock" }
 parking_lot = "0.12"
 sharded_lmdb = { path = "../../sharded_lmdb" }
-spectral = "0.6.0"
 tempfile = "3"
 testutil = { path = "../../testutil" }
 tokio = { version = "1.21", features = ["macros"] }

src/rust/engine/process_execution/docker/src/docker_tests.rs

@@ -8,8 +8,6 @@ use std::time::Duration;
 use bollard::Docker;
 use fs::{RelativePath, EMPTY_DIRECTORY_DIGEST};
 use maplit::hashset;
-use spectral::assert_that;
-use spectral::string::StrAssertions;
 use store::{ImmutableInputs, Store};
 use tempfile::TempDir;
 use testutil::data::{TestData, TestDirectory};
@@ -605,9 +603,9 @@ async fn timeout() {
   assert_eq!(result.original.exit_code, -15);
   let stdout = String::from_utf8(result.stdout_bytes.to_vec()).unwrap();
   let stderr = String::from_utf8(result.stderr_bytes.to_vec()).unwrap();
-  assert_that(&stdout).contains("Calculating...");
-  assert_that(&stderr).contains("Exceeded timeout");
-  assert_that(&stderr).contains("sleepy-cat");
+  assert!(&stdout.contains("Calculating..."));
+  assert!(&stderr.contains("Exceeded timeout"));
+  assert!(&stderr.contains("sleepy-cat"));
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 1)]

src/rust/engine/process_execution/pe_nailgun/Cargo.toml

@@ -32,7 +32,6 @@ maplit = "1.0.1"
 mock = { path = "../../testutil/mock" }
 parking_lot = "0.12"
 sharded_lmdb = { path = "../../sharded_lmdb" }
-spectral = "0.6.0"
 tempfile = "3"
 testutil = { path = "../../testutil" }
 tokio = { version = "1.21", features = ["macros"] }

src/rust/engine/process_execution/remote/Cargo.toml

@@ -44,7 +44,6 @@ maplit = "1.0.1"
 mock = { path = "../../testutil/mock" }
 parking_lot = "0.12"
 sharded_lmdb = { path = "../../sharded_lmdb" }
-spectral = "0.6.0"
 tempfile = "3"
 testutil = { path = "../../testutil" }
 tokio = { version = "1.21", features = ["macros"] }

src/rust/engine/process_execution/remote/src/remote_tests.rs

@@ -14,8 +14,6 @@ use prost::Message;
 use protos::gen::build::bazel::remote::execution::v2 as remexec;
 use protos::gen::google::longrunning::Operation;
 use remexec::{execution_stage::Value as ExecutionStageValue, ExecutedActionMetadata};
-use spectral::prelude::*;
-use spectral::{assert_that, string::StrAssertions};
 use store::{SnapshotOps, Store, StoreError};
 use tempfile::TempDir;
 use testutil::data::{TestData, TestDirectory, TestTree};
@@ -1224,8 +1222,8 @@ async fn server_rejecting_execute_request_gives_error() {
   let error = run_command_remote(mock_server.address(), execute_request)
     .await
     .expect_err("Want Err");
-  assert_that(&error.to_string()).contains("InvalidArgument");
-  assert_that(&error.to_string()).contains("Did not expect this request");
+  assert!(&error.to_string().contains("InvalidArgument"));
+  assert!(&error.to_string().contains("Did not expect this request"));
 }
 
 #[tokio::test]
@@ -1343,7 +1341,7 @@ async fn sends_headers() {
     .iter()
     .map(|received_message| received_message.headers.clone())
     .collect();
-  assert_that!(message_headers).has_length(1);
+  assert_eq!(message_headers.len(), 1);
   for headers in message_headers {
     {
       let want_key = "google.devtools.remoteexecution.v1test.requestmetadata-bin";

src/rust/engine/process_execution/src/local_tests.rs

@@ -7,7 +7,6 @@ use std::time::Duration;
 
 use maplit::hashset;
 use shell_quote::bash;
-use spectral::{assert_that, string::StrAssertions};
 use tempfile::TempDir;
 
 use fs::EMPTY_DIRECTORY_DIGEST;
@@ -568,9 +567,9 @@ async fn timeout() {
   assert_eq!(result.original.exit_code, -15);
   let stdout = String::from_utf8(result.stdout_bytes.to_vec()).unwrap();
   let stderr = String::from_utf8(result.stderr_bytes.to_vec()).unwrap();
-  assert_that(&stdout).contains("Calculating...");
-  assert_that(&stderr).contains("Exceeded timeout");
-  assert_that(&stderr).contains("sleepy-cat");
+  assert!(&stdout.contains("Calculating..."));
+  assert!(&stderr.contains("Exceeded timeout"));
+  assert!(&stderr.contains("sleepy-cat"));
 }
 
 #[tokio::test]