toolbar: improve tab naming

[oliver-sanders]

Follow on from #2023

Presently, tabs are given names like tree or table, fine when you only have one open, not so fine when you have multiple (e.g, is this the tree view I filtered for failed tasks, or the unfiltered one). Log view tabs are particularly problematic.

Consider improvements like:

• Text-editor style name collapsing.
• Replacing view names with icons.
• Displaying in-view options (e.g, "filtered" or " failed").