Fix HermesExecutorFactory build error

[Kudo]

Summary:

7af288e5 introduced a breaking change for whoever importing HermesExecutorFactory.h, because the hermes/inspector-modern/chrome/HermesRuntimeTargetDelegate.h is not a public header. Also the nested import is not ideal for CocoaPods or use_frameworks.
I think HermesRuntimeTargetDelegate could be an implementation detail that hide from header. This PR tries to turn the ownership declaration from std::optional to std::unique_ptr, so that we could hide the concrete type.

Changelog:

[IOS] [FIXED] - Fixed HermesExecutorFactory.h build error when importing its private header

Test Plan:

should introduce no breaking change and ci passed

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	19,495,284	-1
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	22,867,602	-5
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: 362abb9
Branch: main

[facebook-github-bot]

@huntie has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@huntie merged this pull request in 2d46dbe.

[github-actions]

This pull request was successfully merged by @Kudo in 2d46dbe.

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[Kudo]

thanks for merging the fix 🙏