Fixes Gridview JS to respect # in filterUrl

[cebe]

Q	A
Is bugfix?	yes
New feature?	no
Breaks BC?	no
Tests pass?	n/a
Fixed issues	#12836

fixes #12836

[arogachev]

This fix is incorrect. With these filter urls we will get the following results:

• With filter url /posts/index#post: expected - /posts/index#post, actual - /posts/index#post/posts/index#post.
• With filter url /posts/index?foo=1&bar=2#post: expected - /posts/index#post, actual - /posts/index?foo=1&bar=2#post.
• With filter url #post: expected - #post, actual - #post#post.
• With filter url ?foo=1&bar=2#post: expected - #post, actual - ?foo=1&bar=2#post.

I found this during writing of the tests for yii.gridView.js. I've already fixed it and will send PR today.

[arogachev]

hashPos must be used instead of a pos here. Also the anchor needs to be added only when get parameters was cut off, otherwise url already contains anchor and it will lead to duplication again.

[arogachev]

Fully fixed in #13230.