Remove duplication of default field values in iterator-based prop parsing

[rshest]

Summary:
[Changelog][Internal]

This has been on my backlog for some time, submitting the diff to get it out of the way.

It makes the macro-based code in the "iterator-based property parsing" branch somewhat less horrible and less error prone (by removing duplication vs the default values in the class declaration).

Differential Revision: D42990595

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D42990595

[github-actions]

Fails

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📋 Missing Changelog - Can you add a Changelog? To do so, add a "## Changelog" section to your PR description. A changelog entry has the following format: [CATEGORY] [TYPE] - Message. CATEGORY may be: General iOS Android JavaScript Internal (for changes that do not need to be called out in the release notes) TYPE may be: Added, for new features. Changed, for changes in existing functionality. Deprecated, for soon-to-be removed features. Removed, for now removed features. Fixed, for any bug fixes. Security, in case of vulnerabilities. MESSAGE may answer "what and why" on a feature level. Use this to briefly tell React Native users about notable changes.

Generated by 🚫 dangerJS against 4dcfebc

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	8,474,289	+7,889
android	hermes	armeabi-v7a	7,795,948	+8,027
android	hermes	x86	8,950,179	+8,942
android	hermes	x86_64	8,807,843	+8,621
android	jsc	arm64-v8a	9,656,798	+7,885
android	jsc	armeabi-v7a	8,392,041	+8,023
android	jsc	x86	9,720,420	+8,949
android	jsc	x86_64	10,197,080	+8,611

Base commit: 39bdb34
Branch: main

[facebook-github-bot]

This pull request has been merged in 82a7968.