feat: major improvements with sequences

[Seddryck]

• sequences at resource and field levels
• substition of sequences also for non-string fields
• handling of null values

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.16239% with 8 lines in your changes missing coverage. Please review.

Project coverage is 82.61%. Comparing base (e154b5c) to head (fd88e49).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
PocketCsvReader/CsvDataReader.cs	85.00%	0 Missing and 3 partials ⚠️
PocketCsvReader/ArrayOfStringMapper.cs	0.00%	1 Missing ⚠️
...eader/Configuration/ImmutableSequenceCollection.cs	91.66%	1 Missing ⚠️
PocketCsvReader/CsvProfile.cs	90.90%	0 Missing and 1 partial ⚠️
PocketCsvReader/FieldParsing/SequenceSanitizer.cs	85.71%	0 Missing and 1 partial ⚠️
PocketCsvReader/NullableSpan.cs	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
+ Coverage   82.23%   82.61%   +0.38%     
==========================================
  Files          48       58      +10     
  Lines        1396     1490      +94     
  Branches      250      274      +24     
==========================================
+ Hits         1148     1231      +83     
- Misses        175      176       +1     
- Partials       73       83      +10     

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