fix: preserve multipart file part position in requestData

[mathis-m]

Description

when providing type string format binary aka file position is not preserved,
because it is not registered on component mount like all others do.
So the state is later on corrupted,
because when the file is set and so a new property will be added to requestData Map in state.
This results in beeing the last property.
since all other properties' components are registering their value on component mount,
the oder is preserved for those.

Signed-off-by: mathis-m mathis.michel@outlook.de

Motivation and Context

Fixes #6979

How Has This Been Tested?

http://localhost:3200/?url=https://gist.githubusercontent.com/mathis-m/33cfc17fe6e4057702f39651c7aec510/raw/8de7e798e5482069faad5d0595056629810181e7/aUf3bOBB9g.txt

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[tim-lai]

@mathis-m PR merged! Thanks for the fix! Also, that's an interesting tidbit about dispatchInitialValue.