fix: don't raise the blur after focus on a not focusable element

[wentwrong]

Purpose

We shouldn't raise the blur event on an active element after the focus method was called on a not focusable element.

Approach

• add check that if an element is not focusable, then the consecutive blur event is not needed when the focus method was called on this element
• add more strict types

References

DevExpress/testcafe#6236

Pre-Merge TODO

• Write tests for your proposed changes
• Make sure that existing tests do not fail

[wentwrong]

Functional tests are green in related TestCafe PR: DevExpress/testcafe#6236.