Graph view: use initialOptions to save & restore view state on navigation

[markgrahamdawson]

These changes build on the work undertaken to save & restore workspace layout on navigation #1664

Which is part of a larger issue #662

There was an equivalent pull request for the log view #1688
There is an equivalent pull request for the tree view which this builds on: #1705
There is an equivalent pull request for the table view which this builds on: #1711

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• CHANGES.md entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[markgrahamdawson]

It would be nice to get this in so I can finish off #1763

[MetRonnie]

I'm having a bit of a poke about with the Graph view to see if the initial refresh can rely more on Vue's reactivity than manual polling, but this will do for the time being

[markgrahamdawson]

@oliver-sanders If I make a new issue for Ronnies note above.
Can I merge this in? Does it really need a rebase first to tidy up?

pick ee02689 Use initialOptions prop to save view state
pick f07f01b added e2e tests
squash cc5be38 updated change log
squash 0292dc4 fix change log
pick ab5182f Do initial refresh safely when autorefresh is off
squash 816110c added town crier log
squash b0facef reverted CHANGES.md as using towncrier
pick ceecb61 fix empty graph when switching between workflows
pick 3c06b60 added e2e test for 'loads graph when switching between workflows'

[oliver-sanders]

We can also squash-merge PRs (note, you don't need separate commits for changelog, tests, etc, they can go in together with the feature).

[oliver-sanders]

Unfortunately the auto-refresh option appears to be flaky for me. Sometimes the graph comes back, sometimes it does not. I don't think the diff to the refresh method quite did the job.

[markgrahamdawson]

Ready for review...
For testing the autoRefresh setting a console log can be added to the async refresh () function and it should show that - when the component mounts and autorefresh is off - the data polling stops when the nodeDimensions has been calculated.

[oliver-sanders]

Nice.

[oliver-sanders]

@MetRonnie, please check you're happy with new changes and whack the merge button.

[MetRonnie]

Looks like it does the job from my testing out