feat: handle human size prefixes

[iTrooz]

this PR allows you to specify human sizes in the configuration. For example:

[dist]
toolchain_cache_size = "5G"

[cache.disk]
size = "20G"

As a bonus, I also added for lowercase sizes, e.g. "2k"

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 56.75676% with 16 lines in your changes missing coverage. Please review.

Project coverage is 67.18%. Comparing base (7025295) to head (0dafd04).

Files with missing lines	Patch %	Lines
src/config.rs	56.75%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2405      +/-   ##
==========================================
+ Coverage   67.06%   67.18%   +0.11%     
==========================================
  Files          64       64              
  Lines       34718    34747      +29     
==========================================
+ Hits        23285    23345      +60     
+ Misses      11433    11402      -31     

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