Make mat-autocomplete scroll behavior match mat-select.

#### Please describe the feature you would like to request.

Disable the ability to scroll the page when the autocomplete options are displayed, so autocomplete works the same as mat-select.

#### What is the use-case or motivation for this proposal?

Currently when you use mat-autocomplete, the options do not stick to the dropdown field - reported in #12500. The mat-select behavior works great, so could we copy it for mat-autocomplete?

#### Is there anything else we should know?

Looking through the mat-select code, there's 1000 lines of code related to scrolling. I could work on a PR with some pointers to where the behavior is located.

Start by comparing the mat-select scrolling implementation with mat-autocomplete, focusing on how the options remain attached to the dropdown field while the page scrolls. Reproduce the current autocomplete behavior and use the mat-select behavior as the reference. Done means autocomplete prevents page scrolling and keeps its options positioned like mat-select.

Written by the indexing model from the issue text.