Split creation and update logic into two different buttons

In order to have a more granular code, and prevent the browser freezing from having too many lines of code inside a single property, we should have two separate buttons when scheduling a new meeting or editing an existing one.

This has to be done for each meeting type:

- [ ] Informational
- [ ] API Review
- [ ] SDK Review

For more context, see: https://github.com/Azure/azure-sdk-tools/issues/3956

Start by locating the scheduling UI and the creation and editing logic for Informational, API Review, and SDK Review meetings. Separate the actions into distinct buttons for each meeting type, then verify that scheduling new meetings and editing existing ones work without freezing the browser.

Written by the indexing model from the issue text.