Graph hidden branches/tags dropdown: show remote avatar for remote branches if configured

[axosoft-ramint]

We should be using the remote's avatar icon for a remote branch in the dropdown list for the new hidden branches/tags dropdown in the graph toolbar if the avatars are enabled in the graph's settings.

The in-component version of the dropdown (the one in the branch/tag column header) does this already:

[d13]

Resolved with 3590fb1