When list items are removed list.layout is called multiple times can causes a performance issue

[YonatanKra]

Describe the bug
The list-item's disconnected callback triggers the list's layout which triggers the updateItems. This causes a major performance issue with big lists.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://codesandbox.io/s/cool-paper-0k530?file=/src/index.js
2. Open the developer tools in the performance tab and profile
3. Click on the clear everything button
4. Stop profiling
5. See that:
   5.1 layout shift is reported
   5.2 The task takes a huge amount of time (and blocks the UI for that amount of time)

Expected behavior
I'd expect the list items to be removed without a performance overhead.

Screenshots
That's how it looks in the "lab test" from the sandbox example:

This is how it looks in a real life example from an angular application using the mwc-select with mwc-list-item:

Browser Version (please complete the following information):

• OS: MacOS
• Browser Chrome, Brave

**Additional context
There's a need for this amount of items in the select. For instance - to show all the available timezones (around 400 timezones on earth apparently).

[YonatanKra]

Locally I've solved it with debouncing the layout method. It breaks tons of tests (due to the layout method becoming async).

[YonatanKra]

I've created #1928 to show a possible solution for this.
Definitely not complete, but we have a similar solution working in production at the moment.
Would love to sort this out with you.