deprecate persistent_workspaces in favor of persistent-workspaces

[khaneliman]

Closes: #2443

Persistent workspaces currently is the only option using this naming style, changing to match all other options.

Prompt updating config from persistent_workspaces to persistent-workspaces but keep current implementation support until after next release to remove.

Follow up: Update wiki entries to match new name.

[zjeffer]

As I said in the issue, I think we should:

• Make both options parseable
• Log a warning if the user uses the old style
• After a couple of Waybar releases, we should remove the old style.

This way, no existing config would break. If we merge this in the current state, we'd have tons of people opening issues because their configs would break.

[khaneliman]

As I said in the issue, I think we should:

• Make both options parseable
• Log a warning if the user uses the old style
• After a couple of Waybar releases, we should remove the old style.

This way, no existing config would break. If we merge this in the current state, we'd have tons of people opening issues because their configs would break.

@zjeffer This new commit look better? Adds a deprecation warning and allows both configs. We can remove old config style after next release, then.

[zjeffer]

Looks much better! I can't test right now but I'm sure it works fine.

[khaneliman]

Rebased to resolve merge conflicts. Still works fine, like before.

[khaneliman]

@Alexays Should be good to merge, too. Whenever you get a chance.