Add if check before calculating strings for log_debug

[adamkewley]

Fixes issue N/A

Noticed that debug logging takes a bit of CPU during assembly - even if the log is disabled. Turns out, it's because log_debug etc. aren't macros and, therefore, fully evaluate all arguments before forwarding to the logger. If the logger doesn't need to sink the resulting message, then the evaluation is wasted.

Brief summary of changes

• Check if the log level is Debug before computing quantities that may appear in a debug log message

Testing I've completed

• None

Looking for feedback on...

CHANGELOG.md (choose one)

• no need to update because tiny change

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This change is 

[nickbianco]

Good find @adamkewley! Ideally these log statements would be more computationally transparent, but not sure how to make that happen without converting them to macros as you suggested.