sets useInteractionCodeFlow to true in spa samples and test app

adds dynamic signin form to spa samples
sets IdxFeature enum to use human readable strings

export all idx, rename old introspect to introspectAuthn

OKTA-458192
<<<Jenkins Check-In of Tested SHA: b419bd2 for eng_productivity_ci_bot_okta@okta.com>>>
Artifact: okta-auth-js
Files changed count: 51
PR Link: "#1062"

CHANGELOG.md

@@ -18,6 +18,9 @@
 - [#1066](https://github.com/okta/okta-auth-js/pull/1066) Extends type `CookieOptions` from `js-cookie` v3
   - Uses enums for `CookieOptions.sameSite`
   - Removes type `SetCookieOptions`
+- [#1062](https://github.com/okta/okta-auth-js/pull/1062)
+  - Authn method `introspect` is renamed to `introspectAuthn` (still callable as `tx.introspect`)
+  - `IdxFeature` enum is now defined as strings instead of numbers
 
 ### Features