fix: skip log-source-maps for large files

[rigor789]

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What is the current behavior?

Large files in the output directory can crash node/v8.

What is the new behavior?

We skip reading files larger than 50mb as those are unlikely to be source code anyways. This doesn't affect anything but logs - where larger files would just log their actual stack traces rather than a source-mapped one. In practice source would rarely if ever be >50mb though.