Allow to specify attributes without value in selector for HTML filtering rules

There are two cases for this:
- removing elements by matching attributes without values
- removing elements by matching attributes by name only, no matter what their values are

So the rule:

```adguard
example.org$$script[defer]
```

should remove the element:

```html

```

and the rule:

```adguard
example.org$$div[some_attribute]
```

should remove both elements:

```html

Related CoreLibs task: https://github.com/AdguardTeam/CoreLibs/issues/1934