Fix hardcoded stack size and alignment

[Others]

Summary of this PR

Thread stack size is supposed to be determined by a constant in consts.h. A lot of the code in the codebase relies on this, including the code for fetching the a thread's id. However, the assembly code that was really allocating the stack was using a hardcoded value.

This mismatch led to invalid thread id's being returned, and broke increasing stack sizes to avoid stack overflows.

To fix this, I made the assembly dependent on #defines, and made sure those defines were available for those files. I also fixed how those defines were structured in the first place.

Code Quality

As part of this pull request, I've considered the following:

Style:

• [x] Comments adhere to the Style Guide (SG)
• [x] Spacing adhere's to the SG
• [x] Naming adhere's to the SG
• [x] All other aspects of the SG are adhered to, or exceptions are justified in this pull request

Code Craftsmanship:

• [x] I've made an attempt to remove all redundant code
• [x] I've considered ways in which my changes might impact existing code, and cleaned it up
• [x] I've formatted the code in an effort to make it easier to read (proper error handling, function use, etc...)
• [x] I've commented appropriately where code is tricky
• [x] I agree that there is no "throw-away" code, and that code in this PR is of high quality

[Others]

I think this is ready for a review @gparmer. Do I need someone else to look through it too?