Revert "[SVLS-8002] fix: collect CPU metric offsets on PlatformStart (#930)" (#938)

**Please include Jira ticket in title.**

## Overview

## Testing

Author: litianningdatadog

bottlecap/src/lifecycle/invocation/processor.rs

@@ -141,11 +141,15 @@ impl Processor {
             // Resume tmp, fd, and threads enhanced metrics monitoring
             self.enhanced_metrics.resume_usage_metrics_monitoring();
 
+            // Collect offsets for network and cpu metrics
             let network_offset: Option<NetworkData> = proc::get_network_data().ok();
+            let cpu_offset: Option<CPUData> = proc::get_cpu_data().ok();
+            let uptime_offset: Option<f64> = proc::get_uptime().ok();
+
             let enhanced_metric_offsets = Some(EnhancedMetricData {
                 network_offset,
-                cpu_offset: None,
-                uptime_offset: None,
+                cpu_offset,
+                uptime_offset,
             });
             self.context_buffer
                 .add_enhanced_metric_data(&request_id, enhanced_metric_offsets);
@@ -315,23 +319,6 @@ impl Processor {
             .try_into()
             .unwrap_or_default();
         self.context_buffer.add_start_time(&request_id, start_time);
-
-        if self.config.lambda_proc_enhanced_metrics {
-            let cpu_offset: Option<CPUData> = proc::get_cpu_data().ok();
-            let uptime_offset: Option<f64> = proc::get_uptime().ok();
-            if let Some(context) = self.context_buffer.get_mut(&request_id) {
-                if let Some(ref mut enhanced_data) = context.enhanced_metric_data {
-                    enhanced_data.cpu_offset = cpu_offset;
-                    enhanced_data.uptime_offset = uptime_offset;
-                } else {
-                    context.enhanced_metric_data = Some(EnhancedMetricData {
-                        network_offset: None,
-                        cpu_offset,
-                        uptime_offset,
-                    });
-                }
-            }
-        }
     }
 
     #[allow(clippy::too_many_arguments)]

bottlecap/src/metrics/enhanced/lambda.rs

@@ -370,12 +370,6 @@ impl Lambda {
         let uptime = uptime_data_end - uptime_data_offset;
         let total_idle_time = cpu_data_end.total_idle_time_ms - cpu_data_offset.total_idle_time_ms;
 
-        // Change in uptime should be positive and greater than total idle time across all cores
-        if uptime <= 0.0 || (uptime * num_cores) < total_idle_time {
-            debug!("Invalid uptime, skipping CPU utilization metrics");
-            return;
-        }
-
         let mut max_idle_time = 0.0;
         let mut min_idle_time = f64::MAX;
         let now = std::time::UNIX_EPOCH
@@ -389,8 +383,6 @@ impl Lambda {
                 cpu_data_offset.individual_cpu_idle_times.get(cpu_name)
             {
                 let idle_time = cpu_idle_time - cpu_idle_time_offset;
-                let idle_time = idle_time.max(0.0); // Ensure idle time is non-negative
-
                 if idle_time < min_idle_time {
                     min_idle_time = idle_time;
                 }
@@ -402,15 +394,15 @@ impl Lambda {
 
         // Maximally utilized CPU is the one with the least time spent in the idle process
         // Multiply by 100 to report as percentage
-        let cpu_max_utilization = ((uptime - min_idle_time).max(0.0) / uptime) * 100.0;
+        let cpu_max_utilization = ((uptime - min_idle_time) / uptime) * 100.0;
 
         // Minimally utilized CPU is the one with the most time spent in the idle process
         // Multiply by 100 to report as percentage
-        let cpu_min_utilization = ((uptime - max_idle_time).max(0.0) / uptime) * 100.0;
+        let cpu_min_utilization = ((uptime - max_idle_time) / uptime) * 100.0;
 
         // CPU total utilization is the proportion of total non-idle time to the total uptime across all cores
         let cpu_total_utilization_decimal =
-            ((uptime * num_cores) - total_idle_time).max(0.0) / (uptime * num_cores);
+            ((uptime * num_cores) - total_idle_time) / (uptime * num_cores);
         // Multiply by 100 to report as percentage
         let cpu_total_utilization_pct = cpu_total_utilization_decimal * 100.0;
         // Multiply by num_cores to report in terms of cores