Make a few changes to memory usage throughout the application to reduce transient allocations from the `big.txt` test from ~213,000 to ~53,000.
## PR Checklist
* [x] Supports #3075
* [x] I work here.
* [x] Tested manually and WPR'd. Test suite should still pass.
* [x] Am core contributor
## Detailed Description of the Pull Request / Additional comments
Transient allocations are those that are new'd, used, then delete'd. Going back and forth to the system allocator for things we're just going to throw away or use rapidly again is a performance detriment. Not only is it a bunch of time to go ask the system with a syscall, it also hits a whole bunch of locks on the allocators. This PR identifies a few places where we were accidentally allocating and didn't mean to or were allocating and freeing just to turn around and allocate again. I chose other strategies to avoid this.
## Validation Steps Performed
- Ran `big.txt` sample (~6MB file) before and after. Observed heap allocations with WPR.
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