Add structured JSON logging support

[anzheyazzz]

Description of changes:

Add structured JSON logging support to the Ruby RIC, consistent with
the structured logging behavior in other Lambda managed runtimes (Python, Node.js, etc.).

When AWS_LAMBDA_LOG_FORMAT=JSON, each log output is a JSON object containing
at least four key-value pairs:

• timestamp – the time the log message was generated (ISO 8601, UTC)
• level – the log level assigned to the message (DEBUG, INFO, WARN, ERROR, FATAL)
• message – the contents of the log message
• requestId – the unique request ID for the function invocation

This PR includes two commits:

1. fix: Update xray_cause_test for Ruby 3.4+ backtrace format

   • Ruby 3.4+ changed Thread::Backtrace::Location#label from method_name to ClassName#method_name. Use assert_includes to handle both formats.

2. feat: Add structured JSON logging support

   • Add LambdaLogFormatter (JSON mode) with structured fields including exception support
   • Update LoggerPatch to select formatter and log level based on environment variables
   • Refactor TelemetryLogger initialization to apply Logger patch and runtime config before telemetry fd setup
   • Fix LogFormatter (TEXT mode) to append newline for consistency
   • Add unit tests for LambdaLogFormatter, LambdaLogger, and LoggerPatch

Target (OCI, Managed Runtime, both):

Both

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Example Usage:

require 'logger'

def lambda_handler(event:, context:)
    logger = Logger.new($stdout)
    logger.info("Inside the handler function")
end

Output without AWS_LAMBDA_LOG_FORMAT:

I, [2026-03-10T22:30:46.745494 #16] INFO 3244ba10-b213-4742-9cbc-fcc611f42625 -- : Inside the handler function

Output with AWS_LAMBDA_LOG_FORMAT=JSON:

{
	"timestamp":"2026-03-10T21:37:36.350555Z",
	"level":"INFO",
	"message":"Inside the handler function",
	"requestId":"d1491d62-2ed4-4d08-a1be-feea698100f7"
}

Example exceptions:

require 'logger'

def lambda_handler(event:, context:)
    logger = Logger.new($stdout)
    begin
        raise "something went wrong"
    rescue => e
        logger.error(e)
    end
end

Output without AWS_LAMBDA_LOG_FORMAT:

E, [2026-03-10T22:38:29.311464 #16] ERROR f2a7b2cf-ce51-4b7b-b280-a92eea3f8bf5 -- : something went wrong (RuntimeError)
/var/task/lambda_function.rb:5:in 'Object#lambda_handler'
/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric/lambda_handler.rb:28:in 'LambdaHandler#call_handler'
/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:86:in 'AwsLambdaRIC::LambdaRunner#run_user_code'
/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:64:in 'AwsLambdaRIC::LambdaRunner#start_runtime_loop'
/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:47:in 'AwsLambdaRIC::LambdaRunner#run'
/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:235:in 'AwsLambdaRIC::Bootstrap#bootstrap_handler'
/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:217:in 'AwsLambdaRIC::Bootstrap#start'
/var/runtime/index.rb:4:in '<main>'

Output with AWS_LAMBDA_LOG_FORMAT=JSON:

{
	"timestamp":"2026-03-10T22:51:58.675676Z",
	"level":"ERROR",
	"message":"something went wrong",
	"requestId":"f1890346-7a2f-4adf-95de-d90ba9f7d1b8",
	"errorType":"RuntimeError",
	"errorMessage":"something went wrong",
	"stackTrace":["/var/task/lambda_function.rb:6:in 'Object#lambda_handler'","/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric/lambda_handler.rb:28:in 'LambdaHandler#call_handler'","/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:86:in 'AwsLambdaRIC::LambdaRunner#run_user_code'","/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:64:in 'AwsLambdaRIC::LambdaRunner#start_runtime_loop'","/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:47:in 'AwsLambdaRIC::LambdaRunner#run'","/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:235:in 'AwsLambdaRIC::Bootstrap#bootstrap_handler'","/var/runtime/gems/aws_lambda_ric-3.1.3/lib/aws_lambda_ric.rb:217:in 'AwsLambdaRIC::Bootstrap#start'","/var/runtime/index.rb:4:in '<main>'"],
	"location":"/var/task/lambda_function.rb:Object#lambda_handler:6"
}

[trivenay]

Do we rather want to do formatted.encode('UTF-8', invalid: :replace, undef: :replace, replace: '�')

[trivenay]

To not make bad characters fail @maxday ?

[trivenay]

IN this PR I see we are patching both Kernel puts and also logger -> Not this is not usual - For all runtimes we just choose 1 thing and then patch that. For nodejs it's console for python logger. Not sure if we should do both. This is becoming hard to follow. DO we need to patch Kernel.puts?