Fix TypeError crash when token lacks upn and unique_name fields

[Copilot]

When a user's token has neither upn nor unique_name fields, the telemetry code in loginWithBrowser and loginWithBroker crashes with TypeError: Cannot read properties of undefined (reading 'endsWith'), surfacing as an unexpected error during teamsAppExtendToM365.

Change

Added optional chaining (?.) before .endsWith() in both loginWithBrowser and loginWithBroker in packages/vscode-extension/src/commonlib/codeFlowLogin.ts:

// Before — throws if both upn and unique_name are undefined
[TelemetryProperty.Internal]: (
  (tokenJson as any).upn ?? (tokenJson as any).unique_name
).endsWith("@microsoft.com") ? "true" : "false",

// After — safely falls through to "false"
[TelemetryProperty.Internal]: (
  (tokenJson as any).upn ?? (tokenJson as any).unique_name
)?.endsWith("@microsoft.com") ? "true" : "false",