Attempting to clear a file annotation on a split file w/o the annotation no-ops

[eamodio]

Steps to repro:

• Split an editor into 2 tabs so they are side-by-side
• Switch to the left file
• Toggle a file annotation (blame, heatmap, changes, doesn't matter which) in the left file
• Switch to the right file
• 🐛 Attempt to clear the file annotation and nothing will happen

[eamodio]

Since, we can't effectively manage the editor toolbar states (vscode limitation), we will just link the "clear" to clear annotations across all splits of the same editor.

We could also choose to link the editors when turning on the annotations, but I haven't done that because it feels like too much.