Use Mimalloc (#572)

<!-- The PR description should answer 2 (maybe 3) important questions:
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### What

We've had excellent results with this elsewhere, let's try it here.

### How

Import mimalloc, set global allocator.

Cargo.toml

@@ -47,6 +47,7 @@ hyper = "0.14"
 indexmap = "2"
 insta = "1"
 jsonschema = "0.17"
+mimalloc = "0.1"
 multimap = "0.9"
 nonempty = "0.10"
 percent-encoding = "2"

crates/connectors/ndc-postgres/Cargo.toml

@@ -27,6 +27,7 @@ query-engine-translation = { path = "../../query-engine/translation" }
 ndc-sdk = { workspace = true }
 
 async-trait = { workspace = true }
+mimalloc = { workspace = true }
 percent-encoding = { workspace = true }
 prometheus = { workspace = true }
 serde_json = { workspace = true, features = ["raw_value"] }

crates/connectors/ndc-postgres/bin/main.rs

@@ -4,6 +4,9 @@ use ndc_postgres::connector::PostgresSetup;
 use ndc_postgres_configuration::environment::ProcessEnvironment;
 use ndc_sdk::default_main::default_main_with;
 
+#[global_allocator]
+static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;
+
 #[tokio::main]
 pub async fn main() -> ExitCode {
     let result = default_main_with(PostgresSetup::new(ProcessEnvironment)).await;