fix: refactored Str and File classes to use sz_string_view_t

[vardbabayan]

Refactored python/lib.c and replaced all combinations of a pointer and length with sz_string_view_t Covers File and Str structs

[ashvardanian]

Hi @vardbabayan! There are some compilation issues reported on Windows:

      python/lib.c(393): error C2039: 'start': is not a member of 'File'
      python/lib.c(59): note: see declaration of 'File'
      python/lib.c(394): error C2039: 'start': is not a member of 'File'
      python/lib.c(59): note: see declaration of 'File'
      python/lib.c(394): error C2198: 'UnmapViewOfFile': too few arguments for call
      python/lib.c(395): error C2039: 'start': is not a member of 'File'

Can you please patch those before we merge the PR and close the #108?