[3.35] Rename `entryPointBaseUrl` to `entrypointBaseUrl`

[mdebbar]

Blocked on landing in stable

Renaming the entryPointBaseUrl parameter to entrypointBaseUrl.

• PR in the Flutter SDK: https://github.com/flutter/flutter/pull/170166
• Issue: https://github.com/flutter/flutter/issues/168968

cc @piedcipher

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