(fix: #11445) Correct height of autogrow input during resize

[mlesin]

Fixing issue #11445 when autogrow input element doesn't grow during element resizing (see related issue for the example).

It is fixed by conditionally adding QResizeObserver next to native input element: if element doesn't have autogrow property set, no observer is installed to avoid any drop of performance.

What kind of change does this PR introduce?

• [x] Bugfix
• [ ] Feature
• [ ] Documentation
• [ ] Code style update
• [ ] Refactor
• [ ] Build-related changes
• [ ] Other, please describe:

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

The PR fulfills these requirements:

• [x] It's submitted to the dev branch (or v[X] branch)
• [x] When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• [ ] It's been tested on a Cordova (iOS, Android) app
• [ ] It's been tested on an Electron app
• [x] Any necessary documentation has been added or updated in the docs or explained in the PR's description.

If adding a new feature, the PR's description includes:

• [ ] A convincing reason for adding this feature (to avoid wasting your time, it's best to start a new feature discussion first and wait for approval before working on it)

Other information:

[mlesin]

I have no idea why the tests don't pass, such a change should not be the source of this.

[MilosPaunovic]

I have no idea why the tests don't pass, such a change should not be the source of this.

Test are currently failing because there was an internal change intorduced in recent commits. It will be amended soon. You can safely ignore it for this PR.

[xJayMorex]

@mlesin

Could we merge this fix please? In the meantime, is there a workaround for the issue where the height of an autogrow textarea isn't recalculated after resizing the window?