Add toggle to blame UI for whether or not to apply ignore revs file

Handling ignoring of specific files

From gitaly!4177 (closed):

This MR implements keeps a copy of .git-blame-ignore-revs inside of the repository at info/blame-ignore-revs, similar to how .gitattributes and info/attributes work. RawBlame() then checks for the existence of this file and loads it into the git blame command using --ignore-revs-file if it exists.

In the blame view, there will be a new dropdown button Blame preferences.

Default Idle	Prompt for setup	Ignore file in place and toggled on