[Feature]: Allow users to login from embedded Appsmith apps

[infinitetrooper]

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When a private app is embedded into a parent app without an SSO trigger, it currently opens up the login screen. When the user clicks on login, it tries to redirect inside an iFrame which is not possible because of IdP rules.

We should open a new tab to allow user to login to the embedded app instance so that the embedded app will work as Appsmith session will be alive for 30 days and can be shared into an iFrame.