fix(react-native-host): override feature flags for bridgeless mode

[tido64]

Description

Override feature flags for bridgeless mode.

Test plan

This needs to be tested in RNTA:

npm run set-react-version 0.74 -- --core-only
yarn clean
yarn

# Manually apply changes under node_modules/@rnx-kit/react-native-host/

cd example
RCT_NEW_ARCH_ENABLED=1 pod install --project-directory=ios
yarn ios

# In a separate terminal
yarn start

Screenshots