[RUM-5258] RN 0.63 BigInt support

[marco-saia-datadog]

What does this PR do?

Includes a conditional BigInt polyfill, applied for RN 63 when BigInt is undefined.

Motivation

React Native 0.63 does not support BigInt, forcing SDK consumers to apply a polyfill on their side to make the SDK work properly.

Additional Notes

The error that is thrown when the polyfill fails has been introduced for precaution, but it will not be thrown unless executed on a strongly unusual environment.

The reason is that the module big-integer - used for the polyfill - is a dependency of the xcode package, used by React Native CLI.

Therefore, it will be available in pretty much every RN project setup.

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