Preserve flow.json key order across load/save

[turbolent]

Saving a flow.json (e.g. after flow dependencies install) reordered keys alphabetically because every section was a map[string]T and Go's encoding/json sorts map keys on marshal.

Ensure ordering is preserved by adding a generic orderedMap[V] that records insertion order and replays it on MarshalJSON. Every section of jsonConfig embeds it. New entries added programmatically are added at the end of their section instead of being alphabetized between existing keys.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 70.80292% with 40 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
config/json/ordered_map.go	55.29%	31 Missing and 7 partials ⚠️
config/json/contract.go	89.47%	1 Missing and 1 partial ⚠️

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