Update links when files are renamed

[charlespwd]

A LSP Client may give us workspace/didRenameFiles notifications (if they support them).

• For snippet renames, we may update {% render '$oldFileName' ... %} to {% render '$newFileName' %} from all files containing them.
• For asset renames, we may update{{ $oldFileName | asset_url ... }} to {{ $newFileName | asset_url }}
• For section renames, we may update {% section '$oldName' %}

We can do this with the workspace/applyEdit server->client request.

Obsidian & other note taking apps all do something like this, and a "Updated X links in Y files" popup seems like a neat thing to do as well.

[charlespwd]

Oh... I just realized this needs VFS/full theme access.

[charlespwd]

Depends on #521

[charlespwd]

Section (and eventually blocks) is more complicated. I'm going to split it out in a different issue.