Web UI: support SAML app launch URLs

[flyinghermit]

This PR implements <MenuLoginWithActionMenu> button and handles launch URLs for SAML app.

Notable changes:

• <MenuLogin> is updated to handle launchExternalUrl to render <a> tag links instead of with the NavLink. disableSearchAndFilter props specifies to render menu item label instead of the default search/filter input.
• <MenuLoginWithActionMenu> extends <MenuLogin> button and renders similar to <ButtonWithMenu> component. TO support SAML app launch URLs, we need button to show selectable URLs.
• If there are zero launch URL, default <ButtonWithMenu> is displayed with the value of SAML ACS URL. If there is only one launch URL, <ButtonWithMenu> border is displayed with the href value configured with the launch URL value. If there are 1+ launch URL items, <MenuLoginWithActionMenu> is displayed.
• For instances where SAML action button will not be displayed, regular <ButtonBorder> and <MenuLogin> button is displayed with the login items similarly configured as explained above.

The launch URLs can only be configured with tctl. Use this sample spec to configure SAML service provider for testing:

kind: saml_idp_service_provider
metadata:
  name: my_saml_app
spec:
  acs_url: https:/example.com
  entity_id: https:/example.com
  launch_urls:
    - https:/example.com/2
    - https:/example.com/1
version: v1

Note: SAML apps can be launched from Connect but this PR does not cover it. I will follow up separately.

Implements UI for launch URL #46416

[flyinghermit]

both selectable and direct link login button displayed below: