Refactor IDL meta reader

[henry2004y]

• Create new get_file_head() for both ASCII and binary format
• Put end_char and pformat to IDLData properties

[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 7 lines in your changes missing coverage. Please review.

Project coverage is 55.57%. Comparing base (75a7202) to head (6b032ff).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/flekspy/idl/idl.py	90.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
- Coverage   55.88%   55.57%   -0.32%     
==========================================
  Files          12       12              
  Lines        1698     1686      -12     
==========================================
- Hits          949      937      -12     
  Misses        749      749              

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