Use aware time object in `processors.TimeStamper()`

[andrei-korshikov]

At this moment %z, %:z and %Z time format codes are replaced by empty strings (see Note 6), because of:

structlog/src/structlog/processors.py

Lines 528 to 529 in 768931a

	# A naive local datetime is fine here, because we only format it.
	return datetime.datetime.now() # noqa: DTZ005

Could you replace datetime.datetime.now() with datetime.datetime.now().astimezone()?

And, frankly, I disagree with the comment: I use aware time object here exactly because I format it (using %:z in my case).

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Off-topic: thank you for attrs and structlog! And huuuge thanks for your articles—I've learned from your texts a lot.