[Android] Fix return type marshalling on IsKeyStorePrivateKeyEntry

[simonrozsival]

This PR addresses #103337 (comment): the C code returns int32_t and the managed side specified wrong type.

/cc @akoeplinger @vcsjones

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[simonrozsival]

/azp run runtime-extra-platforms

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[akoeplinger]

Should we fix the rest of the cases that use UnmanagedType.U1?
https://github.com/search?q=repo%3Adotnet%2Fruntime+UnmanagedType.U1+path%3Asrc%2Flibraries%2FCommon%2Fsrc%2FInterop%2FAndroid&type=code

[vcsjones]

@akoeplinger

Should we fix the rest of the cases that use UnmanagedType.U1?

Those are existing p/invokes, and they "work" given that the C-bool we are using happen to be 1-byte.

This is a clear mismatch though. I think we should backport this PR to release/9.0-preview6. So perhaps it would make sense to keep this PR focused to make the backport to the release branch as easy as possible, and the others can be cleaned up in a separate PR.

[simonrozsival]

The failing runtime-extra-platforms tests are unrelated