Update metadata spec regarding ECS/Fargate pod UIDs

[z1c0]

Description

A recent issue showed that the current spec for parsing Kubernetes pod UIDs does not cover Amazon ECS/Fargate. The existing regex patterns need to be extended.

Spec Issue

• [META 676] Spec: Update metadata spec regarding ECS/Fargate pod UIDs #677

Agent Issues

• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-java#2762
• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-dotnet#1805
• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-nodejs#2898
• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-python#1621
• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-go#1303
• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-php#756
• [META 676] Update metadata spec regarding ECS/Fargate pod UIDs apm-agent-ruby#1297