fix: ensure msal public client application is initialized

[gavinbarron]

Closes #

PR Type

• Bugfix

Description of the changes

adds an awaited initialize check to the Msal2Provider initialize method
This is required in MSAL v3
This change should allow Anglar16 developers to use the msal-angular v3 package to create and pass in a public client application.
It's compatible with msal-browser v2 as the initialize method exists with the same signature on the PublicClientApplication class in that version.

When merged we will need to do additional testing with an Angular16 project to detect any other issues which may require us publishing an @microsoft/mgt-msal3-provider package for clean version separation and support.

PR checklist

• Project builds (yarn build) and changes have been tested in at least two supported browsers (Edge + non-Chromium based browser)
• All public APIs (classes, methods, etc) have been documented following the jsdoc syntax
• Stories have been added and existing stories have been tested
• Added appropriate documentation. Docs PR:

• License header has been added to all new source files (yarn setLicense)
• Contains NO breaking changes

Other information

[microsoft-github-policy-service]

Thank you for creating a Pull Request @gavinbarron.

This is a checklist for the PR reviewer(s) to complete before approving and merging this PR:

• I have verified a documentation PR has been linked and is approved (or not applicable)
• I have ran this PR locally and have tested the fix/feature
• I have verified that stories have been added to storybook (or not applicable)
• I have tested existing stories in storybook to verify no regression has occured
• I have tested the solution in at least two browsers (Edge + 1 non-Chromium based browser)