[heft] Stop using true-case-path

[dmichon-msft]

Summary

Remove usage of true-case-path in Heft.

Details

The implementation of true-case-path performs directory enumeration of every folder between the file system root and heft's working directory. Usage of this tool was motivated by issues with drive letter casing normalization on Windows, but the implementation of doing so in true-case-path is just a hardcoded "if on Windows, uppercase the drive letter", so we may as well just do the same directly.

The directory enumerations cause problems when running inside of build systems that monitor file system accesses, since they cause the system to see the process as enumerating root-level folders.

How it was tested

The pipelines for this PR cover Heft sufficiently.

Impacted documentation

None.