Use copy_from_slice() over clone_from_slice() for u8 slice copies

[steviez]

Problem

clone_from_slice() would hypothetically visit each item in the slice and clone it whereas copy_from_slice() can memcpy the whole slice in one go.

Technically, Rust does the right thing for us by making clone_from_slice() defer to copy_from_slice() for types that implement Copy trait. However, we should still use the more efficient method directly to show intent.

Summary of Changes

Use copy_from_slice() over clone_from_slice() for &[u8] copies.

As mentioned, Rust made it such that copy_from_slice() would get called in this instance starting from v1.52.0 as evidenced in this commit: rust-lang/rust@130fb243bd9e

[codecov]

Codecov Report

Merging #33536 (d3acfeb) into master (144e6d6) will decrease coverage by 0.1%.
Report is 17 commits behind head on master.
The diff coverage is 100.0%.

@@            Coverage Diff            @@
##           master   #33536     +/-   ##
=========================================
- Coverage    81.7%    81.7%   -0.1%     
=========================================
  Files         802      802             
  Lines      217872   217872             
=========================================
- Hits       178146   178127     -19     
- Misses      39726    39745     +19     

[CriesofCarrots]

Thanks!