perf: fix loader memory leak from non-destroyed source map consumers

[pmmmwh]

This fixes a memory leak in the loader when source map generation is required - it will now properly cleanup instances of SourceMapConsumer and maintain decent performance when the number of files increases.

Fixes #255
Fixes #524
Fixes #536

[serkanyersen]

Thanks for the fix! I've tested this locally and it works. However, I think SourceMapConsumer.with is adding some overhead :/

my local test results show this

SourceMapConsumer.with	consumer.destroy()
2 minutes	1.70 - 1.80 minutes

I think the size of our repo is amplifying whatever overhead with function has. Looking at their implementation I couldn't identify anything specific, it could just be the added delay on calling the destroy

This is an output of 1-2 runs though. can you give me some time to benchmark them with hyperfine. I'll let you know by tomorrow.

[serkanyersen]

Never mind, it was just my computer being weird. they are the same. 😄