[TextInputLayout] End Clear Icon visibility not backward compatible

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**Description:**

I have `TextInputLayout`+`TextInputEditText` combo; `TextInputLayout` styled to `@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox` and `app:endIconMode="clear_text"`, while `TextInputEditText` has:

```xml
android:background="@null"
android:cursorVisible="false"
android:inputType="textNoSuggestions"
android:clickable="true"
android:focusable="false"
android:focusableInTouchMode="false"
```

The control is setup so that users can't directly entry text, the editText has a click listener that opens a drop-down or date-picker, that populates the editText once user have selected something. The end clear button should be visible to allow for clearing the data. This worked in `material-1.3.0`, the clear button is showing up even if the field is not focusable, but not longer shows up in `material-1.4.0-x`. There's a certain weirdness in 1.4.0-x as well, in that if the `focusable=false` then the clear button doesn't exist, but if `focusable=true` then it's clickable but alpha=0f, so not really visible to the human eye, even if it participates in the measure pass.

**Expected behavior:**

Would like the clear button to be visible and useable when the `TextInputEditText` is customised to work like a dropdown button. Would prefer not to use an actual button for this because the UX is weird, especially if user wants to clear the data, clear button is the obvious UX.

**Android API version:** 29

**Material Library version:** Reproducible on `material-1.4.0-rc01` and `material-1.4.0-beta01`, worked as normal in `material-1.3.0`.

**Device:** tested and shows up on API 25 onwards