Inconsistent rendering of amp-autocomplete

### Description

Amp-autocomplete renders the associated input field differently, depending on browser and/or if it uses amp-moustache. In chromium based browsers the close button (x) is sometimes displayed inside the INPUT element (if autocomplete uses amp-moustache template), while in Firefox it is never displayed.

Also I have been unable to find a way NOT to display the close button, as it interferes with a custom icon used in input fields I am working on.

### Reproduction Steps

https://amp.dev/documentation/examples/components/amp-autocomplete/?format=websites

Compare your example page in Chrome and Firefox. In Firefox the (x) close button is never displayed, while in Chrome it's sometimes displayed, sometimes not.

Chromium (106.0.5249.91):

Firefox (105.0.1):

### Relevant Logs

_No response_

### Browser(s) Affected

Chrome, Firefox

### OS(s) Affected

Linux

### Device(s) Affected

_No response_

### AMP Version Affected

2209142312000

Start with the amp-autocomplete example at https://amp.dev/documentation/examples/components/amp-autocomplete/?format=websites and reproduce the input rendering in Chrome and Firefox on Linux. Investigate the differing close-button behavior, including the amp-moustache case and the custom-icon conflict; the issue is resolved when rendering is consistent and the close button can be omitted.

Written by the indexing model from the issue text.