feat: Add support for DD_LOGS_ENABLED as alias for DD_SERVERLESS_LOGS_ENABLED

[litianningdatadog]

https://datadoghq.atlassian.net/browse/SVLS-7818

Overview

Add DD_LOGS_ENABLED environment variable and YAML config option as an alias for DD_SERVERLESS_LOGS_ENABLED. Both variables now use OR logic, meaning logs are enabled if either variable is set to true.

Changes:

• Add logs_enabled field to EnvConfig and YamlConfig structs
• Implement OR logic in merge_config functions: logs are enabled if either DD_LOGS_ENABLED or DD_SERVERLESS_LOGS_ENABLED is true
• Add comprehensive test coverage with 9 test cases covering all combinations of the two variables
• Maintain backward compatibility with existing configurations
• Default value remains true when neither variable is set

Testing

Set DD_LOGS_ENABLED and DD_SERVERLESS_LOGS_ENABLED to false and expect:

• Log can be found in AWS console
• Log could NOT be found in DD console

Otherwise the log should be available in DD console.