Dialog: «Close» button located at the end of the dialog window and caption is not marked as heading

[PosikBoy]

Describe the bug

1. The close button is positioned at the end of the DOM tree. When a screen reader user navigates into the dialog, they must tab through numerous elements before reaching it, creating a poor user experience.
   I suggest moving the close button to the top of the dialog window.

2. Heading in dialog not marked as heading
   Suggest mart it as h2

Reproduction

https://stackblitz.com/edit/gravity-ui-uikit-example-camd3mlr?file=src%2FApp.tsx

Steps to reproduce

No response

Environment

macos, yandexBrowaer

Validations

• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• The provided reproduction is a minimal reproducible example of the bug.