Replace once_cell with std::sync::LazyLock in aws-sigv4 (#4050)

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here -->
Replaces an external dependency with functionality provided by `std`

## Description
<!--- Describe your changes in detail -->

## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] For changes to the AWS SDK, generated SDK code, or SDK runtime
crates, I have created a changelog entry Markdown file in the
`.changelog` directory, specifying "aws-sdk-rust" in the `applies_to`
key.

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

---------

Co-authored-by: Landon James <lnj@amazon.com>

Author: FalkWoldmann

.changelog/1742160441.md

@@ -0,0 +1,11 @@
+---
+applies_to:
+- aws-sdk-rust
+authors:
+- FalkWoldmann
+references: []
+breaking: false
+new_feature: false
+bug_fix: false
+---
+Removes the once_cell crate from the aws-sigv4 crate

.changelog/1742673776.md

@@ -0,0 +1,12 @@
+---
+applies_to:
+- client
+- server
+authors:
+- FalkWoldmann
+references: []
+breaking: false
+new_feature: false
+bug_fix: false
+---
+Removes the once_cell crate from the rust-runtime crates

.changelog/1742674486.md

@@ -0,0 +1,11 @@
+---
+applies_to:
+- aws-sdk-rust
+authors:
+- FalkWoldmann
+references: []
+breaking: false
+new_feature: false
+bug_fix: false
+---
+Removes the once_cell crate from the `rust-runtime` crate

.changelog/1742674773.md

@@ -0,0 +1,10 @@
+---
+applies_to: []
+authors:
+- FalkWoldmann
+references: []
+breaking: false
+new_feature: false
+bug_fix: false
+---
+Removes the once_cell crate from the tools crates

aws/rust-runtime/Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "aws-runtime"
-version = "1.5.6"
+version = "1.5.7"
 authors = ["AWS Rust SDK Team <aws-sdk-rust@amazon.com>"]
 description = "Runtime support code for the AWS SDK. This crate isn't intended to be used directly."
 edition = "2021"
@@ -31,7 +31,6 @@ http-02x = { package = "http", version = "0.2.9" }
 http-body-04x = { package = "http-body", version = "0.4.5" }
 http-1x = { package = "http", version = "1.1.0", optional = true }
 http-body-1x = { package = "http-body", version = "1.0.0", optional = true }
-once_cell = "1.20.1"
 percent-encoding = "2.3.1"
 pin-project-lite = "0.2.14"
 regex-lite = { version = "0.1.5", optional = true }

aws/rust-runtime/aws-config/Cargo.lock

@@ -5,10 +5,10 @@
 
 use crate::sdk_feature::AwsSdkFeature;
 use aws_smithy_runtime::client::sdk_feature::SmithySdkFeature;
-use once_cell::sync::Lazy;
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::fmt;
+use std::sync::LazyLock;
 
 const MAX_COMMA_SEPARATED_METRICS_VALUES_LENGTH: usize = 1024;
 #[allow(dead_code)]
@@ -92,8 +92,8 @@ impl Iterator for Base64Iterator {
     }
 }
 
-pub(super) static FEATURE_ID_TO_METRIC_VALUE: Lazy<HashMap<BusinessMetric, Cow<'static, str>>> =
-    Lazy::new(|| {
+pub(super) static FEATURE_ID_TO_METRIC_VALUE: LazyLock<HashMap<BusinessMetric, Cow<'static, str>>> =
+    LazyLock::new(|| {
         let mut m = HashMap::new();
         for (metric, value) in BusinessMetric::iter()
             .cloned()

aws/rust-runtime/aws-runtime/Cargo.toml

@@ -5,12 +5,12 @@
 
 //! Utilities for testing the User-Agent header
 
-use once_cell::sync::Lazy;
 use regex_lite::Regex;
+use std::sync::LazyLock;
 
 // regular expression pattern for base64 numeric values
 #[allow(dead_code)]
-static RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"m/([A-Za-z0-9+/=_,-]+)").unwrap());
+static RE: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"m/([A-Za-z0-9+/=_,-]+)").unwrap());
 
 /// Asserts `user_agent` contains all metric values `values`
 ///

aws/rust-runtime/aws-runtime/src/user_agent/metrics.rs

@@ -1,6 +1,6 @@
 [package]
 name = "aws-sigv4"
-version = "1.3.0"
+version = "1.3.1"
 authors = ["AWS Rust SDK Team <aws-sdk-rust@amazon.com>", "David Barsky <me@davidbarsky.com>"]
 description = "SigV4 signer for HTTP requests and Event Stream messages."
 edition = "2021"
@@ -28,7 +28,6 @@ hex = "0.4.3"
 hmac = "0.12"
 http0 = { version = "0.2.9", optional = true, package = "http" }
 http = { version = "1.1.0", optional = true }
-once_cell = "1.20.1"
 p256 = { version = "0.11", features = ["ecdsa"], optional = true }
 percent-encoding = { version = "2.3.1", optional = true }
 ring = { version = "0.17.5", optional = true }