Add LocalEnvironment using stdout

[02strich]

So far the DefaultEnvironment was hard coded to use the agent sink as that
was the recommendation for workloads on-premise.

While a fair recommendation, it isn't accurate for all workloads. This
adds a similer local environment that uses the StdoutSink instead of the agent sink
for such customers.

Issue #, if available:

Description of changes:

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[jaredcnance]

Thanks for the PR! I'll need to take a closer look at this for breaking changes. 1 other comment below.

[jaredcnance]

👍

[jaredcnance]

In the other implementations, we provide a LocalEnvironment for this purpose. Would that meet your needs here? Any particular reason to depart from that pattern?

https://github.com/awslabs/aws-embedded-metrics-node/blob/master/src/environment/LocalEnvironment.ts#L58

[02strich]

Oh, I had not seen that (my need is python-only). My thinking was to maximize code re-use as DefaultEnvironment is almost exactly what was needed. I can change it to call it LocalEnvironment to be consistent though 👍

[02strich]

So made this change and now the test is happy as well :)

[02strich]

@jaredcnance if you got some time to have another look would be great

[hussam789]

PR Code Suggestions ✨

Category	Suggestion	Impact
General	Ensure output is flushed The accept method should flush stdout after printing to ensure metrics are immediately visible, especially in containerized environments where output buffering can occur. aws_embedded_metrics/sinks/stdout_sink.py [24-27] def accept(self, context: MetricsContext) -> None: for serialized_content in self.serializer.serialize(context): if serialized_content: - print(serialized_content) + print(serialized_content, flush=True) Apply this suggestion Suggestion importance[1-10]: 5 __ Why: The change to add flush=True to the print statement helps to ensure immediate output, which is beneficial in buffered or containerized environments, representing a modest but useful improvement.	Low
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