feat: upgrade nginx version and add downloads configuration(MAPCO-10121)

[almog8k]

This pull request updates the Helm chart and NGINX configuration to improve modularity, upgrade dependencies, and enhance observability. The changes separate the downloads server configuration, modernize the NGINX image and dependencies, and introduce OpenTelemetry tracing support.

NGINX and Helm Chart Improvements:

• Upgraded the nginx Helm dependency to version 2.1.1 and changed the repository to common, ensuring use of the latest, standardized NGINX chart. (helm/Chart.yaml)
• Updated the NGINX image to common/nginx:v2.1.0 for consistency and access to newer features. (helm/values.yaml)

Configuration Refactoring and Modularity:

• Extracted the /downloads server block configuration into a dedicated downloads.conf file, improving modularity and clarity in NGINX configuration. (helm/config/downloads.conf, helm/config/nginx.conf, helm/templates/nginx/nginx-configmap.yaml, helm/values.yaml) [1] [2] [3]
• Adjusted volume mounts and configmap templates to include the new downloads.conf file. (helm/values.yaml, helm/templates/nginx/nginx-configmap.yaml) [1] [2]

Observability and Logging Enhancements:

• Integrated OpenTelemetry tracing into the NGINX configuration, allowing for distributed tracing and improved monitoring. (helm/config/nginx.conf, helm/values.yaml) [1] [2]
• Simplified log format management by moving the log format definition to a separate log_format.conf file and switching the access log to use the main format. (helm/config/nginx.conf)

Ingress and Service Configuration:

• Refactored ingress configuration to use ingressClassName, support additional annotations, and provide a more flexible mapping structure. (helm/values.yaml)