Significantly faster BIOS exports

[ScrubN]

Although still not optimal, this drops BIOS export times from almost a minute to less than a second.

• Because File.WriteAllBytes overwrites the file if it exists, only the final write is needed.
• Additionally, I rewrote PatternAt to use spans instead of LINQ, which removes 2 heap allocations per comparison (from Skip and Take) and uses a SIMD vectorized comparison function instead of the while-loop based sequence compare from LINQ.

[syntaxsdev]

lgtm

[G2G2G2G]

great changes mate, there can always be a better wheel ;)