Merge Lambda Managed Instance feature branch (#947)

https://datadoghq.atlassian.net/browse/SVLS-8080

## Overview
Merge Lambda Managed Instance feature branch

## Testing 
Covered by individual commits

Co-authored-by: shreyamalpani <shreya.malpani@datadoghq.com>
Co-authored-by: duncanista <30836115+duncanista@users.noreply.github.com>
Co-authored-by: astuyve <aj.stuyvenberg@datadoghq.com>
Co-authored-by: jchrostek-dd <john.chrostek@datadoghq.com>
Co-authored-by: tianning.li <tianning.li@datadoghq.com>

Author: 5 people

aws.rs

@@ -11,6 +11,9 @@ const AWS_LAMBDA_FUNCTION_NAME: &str = "AWS_LAMBDA_FUNCTION_NAME";
 const AWS_LAMBDA_RUNTIME_API: &str = "AWS_LAMBDA_RUNTIME_API";
 const AWS_LWA_LAMBDA_RUNTIME_API_PROXY: &str = "AWS_LWA_LAMBDA_RUNTIME_API_PROXY";
 const AWS_LAMBDA_EXEC_WRAPPER: &str = "AWS_LAMBDA_EXEC_WRAPPER";
+const AWS_LAMBDA_INITIALIZATION_TYPE: &str = "AWS_LAMBDA_INITIALIZATION_TYPE";
+
+pub const LAMBDA_MANAGED_INSTANCES_INIT_TYPE: &str = "lambda-managed-instances";
 
 #[allow(clippy::module_name_repetitions)]
 #[derive(Debug, Clone)]
@@ -21,6 +24,7 @@ pub struct AwsConfig {
     pub runtime_api: String,
     pub sandbox_init_time: Instant,
     pub exec_wrapper: Option<String>,
+    pub initialization_type: String,
 }
 
 impl AwsConfig {
@@ -33,8 +37,15 @@ impl AwsConfig {
             runtime_api: env::var(AWS_LAMBDA_RUNTIME_API).unwrap_or_default(),
             sandbox_init_time: start_time,
             exec_wrapper: env::var(AWS_LAMBDA_EXEC_WRAPPER).ok(),
+            initialization_type: env::var(AWS_LAMBDA_INITIALIZATION_TYPE).unwrap_or_default(),
         }
     }
+
+    #[must_use]
+    pub fn is_managed_instance_mode(&self) -> bool {
+        self.initialization_type
+            .eq(LAMBDA_MANAGED_INSTANCES_INIT_TYPE)
+    }
 }
 
 #[allow(clippy::module_name_repetitions)]

flush_strategy.rs

@@ -21,6 +21,20 @@ pub enum FlushStrategy {
     Continuously(PeriodicStrategy),
 }
 
+impl FlushStrategy {
+    /// Returns the name of the flush strategy as a string slice.
+    #[must_use]
+    pub const fn name(&self) -> &'static str {
+        match self {
+            FlushStrategy::Default => "default",
+            FlushStrategy::End => "end",
+            FlushStrategy::Periodically(_) => "periodically",
+            FlushStrategy::EndPeriodically(_) => "end-periodically",
+            FlushStrategy::Continuously(_) => "continuously",
+        }
+    }
+}
+
 // A restricted subset of `FlushStrategy`. The Default strategy is now allowed, which is required to be
 // translated into a concrete strategy.
 #[allow(clippy::module_name_repetitions)]
@@ -121,4 +135,34 @@ mod tests {
         let flush_strategy: FlushStrategy = serde_json::from_str("\"end,invalid\"").unwrap();
         assert_eq!(flush_strategy, FlushStrategy::Default);
     }
+
+    #[test]
+    fn test_flush_strategy_name_default() {
+        let strategy = FlushStrategy::Default;
+        assert_eq!(strategy.name(), "default");
+    }
+
+    #[test]
+    fn test_flush_strategy_name_end() {
+        let strategy = FlushStrategy::End;
+        assert_eq!(strategy.name(), "end");
+    }
+
+    #[test]
+    fn test_flush_strategy_name_periodically() {
+        let strategy = FlushStrategy::Periodically(PeriodicStrategy { interval: 1000 });
+        assert_eq!(strategy.name(), "periodically");
+    }
+
+    #[test]
+    fn test_flush_strategy_name_end_periodically() {
+        let strategy = FlushStrategy::EndPeriodically(PeriodicStrategy { interval: 2000 });
+        assert_eq!(strategy.name(), "end-periodically");
+    }
+
+    #[test]
+    fn test_flush_strategy_name_continuously() {
+        let strategy = FlushStrategy::Continuously(PeriodicStrategy { interval: 30000 });
+        assert_eq!(strategy.name(), "continuously");
+    }
 }