Replace typedef with using

[marcosbento]

Description

Modernise and consolidate the code base by systematically using using instead of typedef to introduce type aliases.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 64.28571% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.81%. Comparing base (f9167ba) to head (c97993d).

Files with missing lines	Patch %	Lines
src/eckit/os/SharedInt.cc	0.00%	2 Missing ⚠️
src/eckit/sql/SQLTable.cc	0.00%	2 Missing ⚠️
src/eckit/io/Offset.cc	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #239   +/-   ##
========================================
  Coverage    65.81%   65.81%           
========================================
  Files         1133     1133           
  Lines        57484    57484           
  Branches      4340     4340           
========================================
  Hits         37833    37833           
  Misses       19651    19651           

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