[CHORE] Improve core package iOS podspec compatibility

[marco-saia-datadog]

What does this PR do?

Introduces an additional check to verify if install_modules_dependencies exists before calling it.

When the method does not exist on new architecture, we assume that RN version is < 0.71 and show a message to warn users that we don't officially support new architecture for RN < 0.71.

Additional Notes

The check was not introduced before as we don't officially support the new architecture on React Native versions below 0.71, and we were only checking for RCT_NEW_ARCH_ENABLED == 1, since the install_modules_dependencies method has been introduced in RN 0.71.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change