(feat): adopt Go 1.23 stdlib and add iter.Seq APIs

[napalu]

Bump go.mod to 1.23. Replace hand-rolled utils with stdlib (slices, maps, cmp, min). Add iter.Seq iterators to OrderedMap, Queue, and Parser. Clean up internal code.

[codecov]

Codecov Report

❌ Patch coverage is 80.42553% with 46 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.52%. Comparing base (8a79e04) to head (95f250b).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
v2/goopt_internal.go	74.69%	20 Missing and 1 partial ⚠️
v2/help_parser.go	50.00%	8 Missing and 3 partials ⚠️
v2/goopt.go	90.32%	0 Missing and 6 partials ⚠️
v2/types/orderedmap/ordered_map.go	70.00%	3 Missing and 3 partials ⚠️
v2/types/queue/q.go	81.81%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #134      +/-   ##
==========================================
- Coverage   79.57%   79.52%   -0.06%     
==========================================
  Files          88       87       -1     
  Lines       13359    13340      -19     
==========================================
- Hits        10631    10608      -23     
- Misses       2001     2002       +1     
- Partials      727      730       +3     

Flag	Coverage Δ
v1	74.74% <ø> (ø)
v2	82.13% <80.42%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
v2/argument_config_funcs.go	100.00% <100.00%> (ø)
v2/command_config_funcs.go	89.79% <100.00%> (ø)
v2/goopt_internal_positionals.go	93.36% <100.00%> (-0.10%)	⬇️
v2/i18n/bundle.go	72.24% <100.00%> (-0.46%)	⬇️
v2/internal/parse/state.go	94.73% <100.00%> (ø)
v2/internal/parse/tag_accept.go	89.89% <100.00%> (ø)
v2/internal/parse/tag_depend.go	88.30% <100.00%> (ø)
v2/internal/parse/tag_validators.go	95.83% <100.00%> (ø)
v2/internal/util/numeric.go	70.00% <ø> (-11.82%)	⬇️
v2/internal/util/strings.go	100.00% <100.00%> (ø)
... and 6 more

Files with missing lines	Coverage Δ
v2/argument_config_funcs.go	100.00% <100.00%> (ø)
v2/command_config_funcs.go	89.79% <100.00%> (ø)
v2/goopt_internal_positionals.go	93.36% <100.00%> (-0.10%)	⬇️
v2/i18n/bundle.go	72.24% <100.00%> (-0.46%)	⬇️
v2/internal/parse/state.go	94.73% <100.00%> (ø)
v2/internal/parse/tag_accept.go	89.89% <100.00%> (ø)
v2/internal/parse/tag_depend.go	88.30% <100.00%> (ø)
v2/internal/parse/tag_validators.go	95.83% <100.00%> (ø)
v2/internal/util/numeric.go	70.00% <ø> (-11.82%)	⬇️
v2/internal/util/strings.go	100.00% <100.00%> (ø)
... and 6 more

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