refactor: minor refactorings in package hash

[ci42]

• removed duplicated code for constant time hash comparison
• removed unnecessary type conversions
• always return the same error value if hash and password don't match(hash.ErrMismatchedHashAndPassword)

Checklist

• I have read the contributing guidelines.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.

[codecov]

Codecov Report

Merging #3186 (7ea7315) into master (5535fcb) will decrease coverage by 0.24%.
The diff coverage is 100.00%.

❗ Current head 7ea7315 differs from pull request most recent head f29dbd0. Consider uploading reports for the commit f29dbd0 to get more accurate results

@@            Coverage Diff             @@
##           master    #3186      +/-   ##
==========================================
- Coverage   78.13%   77.89%   -0.24%     
==========================================
  Files         325      320       -5     
  Lines       20811    20466     -345     
==========================================
- Hits        16260    15943     -317     
+ Misses       3340     3324      -16     
+ Partials     1211     1199      -12     

Impacted Files	Coverage Δ
hash/hash_comparator.go	85.56% <100.00%> (-0.06%)	⬇️
hash/hasher_argon2.go	70.37% <100.00%> (ø)

... and 34 files with indirect coverage changes

[aeneasr]

LGTM - thanks!