Allow configuration of property casing convention for automatic properties

[jaredcnance]

We automatically add some properties for each environment:

aws-embedded-metrics-java/src/main/java/software/amazon/cloudwatchlogs/emf/environment/LambdaEnvironment.java

Lines 60 to 65 in 9875fed

	public void configureContext(MetricsContext context) {
	addProperty(context, "executionEnvironment", getEnv(AWS_EXECUTION_ENV));
	addProperty(context, "functionVersion", getEnv(LAMBDA_FUNCTION_VERSION));
	addProperty(context, "logStreamId", getEnv(LAMBDA_LOG_STREAM));
	getSampledTrace().ifPresent(traceId -> addProperty(context, "traceId", traceId));
	}

If customers are emitting similar properties from a different LogGroup, it can be cumbersome to correlate them. For example, if the customer is using Lambda Insights (which uses snake case), they would have to query data like:

filter requestId = "X" or request_id = "X"
# OR
fields coalesce(requestId, request_id) as req 
| filter req = "X"

Instead, we could offer a configuration parameter that defines the convention this library uses. For example:

AWS_EMF_CASE_CONVENTION=snake