feat(experimentalIdentityAndAuth): enable identity and auth by default

[syall]

Dependent on:

• 1321

• 1322

• 1323

• 1324

• 1325

• This PR should be rebased after the dependent PRs are merged

experimentalIdentityAndAuth behavior is now the default auth behavior.

The experimentalIdentityAndAuth flag is now oppositely replaced with useLegacyAuth, which enables legacy auth behavior for backward compatibility concerns.