[login][msal2.0] multi-login templating support

[vogtn]

Describe the bug The multi-login experience should support templating as defined in the spec: https://github.com/microsoftgraph/microsoft-graph-toolkit/blob/main/specs/mgt-login.md#templates

Additional context #46

[ghost]

Hello vogtn, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌