Drag and drop: 'dragleave' event fires when mouse still over node.

[liesahead]

Minimal reproduction of the bug/regression with instructions:

When moving mouse over node in drag mode sometimes dragleave fires (and it is followed by immediate 'dragover' again) which is causing classname is-dragging-over to reapply. And as we have background color change applied for is-dragging-over our node is blinking on drag which looks buggy. Here is a gif attached.

Expected behavior:

'is-dragging-over' is not reapplied when still over node.

Versions of Angular Tree Component, Angular, Node, affected browser(s) and operating system(s):

"@angular/animations": "^12.2.11",
"@angular/cdk": "^12.2.11",
"@angular/common": "^12.2.11",
"@angular/compiler": "^12.2.11",
"@angular/core": "^12.2.11",
"@angular/flex-layout": "12.0.0-beta.35",
"@angular/forms": "^12.2.11",
"@angular/material": "^12.2.11",
"@angular/platform-browser": "^12.2.11",
"@angular/platform-browser-dynamic": "^12.2.11",
"@angular/router": "^12.2.11",
"@angularclass/hmr": "^3.0.0",
"@circlon/angular-tree-component": "11.0.4",

Browser: Chrome Version 95.0.4638.69 (Official Build) (64-bit)
OS: Windows 10 latest
Node: v14.17.5

Other information:

Probably could be fixed by #927

I would be willing to submit a PR to fix this issue

[ ] Yes (Assistance will be provided if you need help to submit a pull request)
[X ] No