Fix tab panel initial tab selection

[talldan]

What?

Fixes #47079

Why?

From what I can tell there are two causes of the bug:

1. The Navigation block's List View tab isn't declared on first render, it only becomes present in the tabs array on later renders.
2. The TabPanel no longer supports lazily adding initial tabs after TabPanel: Add prop to allow disabling of a tab button #46471, it now always falls back to the first enabled tab in the tabs array.

I did try looking to see if this could be fixed by always rendering the tab navigation block, but it's less than straightforward. The tab is added somewhat dynamically when there are fills in a slot. I struggled to see where the issue was coming from.

How?

This fixes the issue. If initalTabName is declared, but there's no matching tab in the tabs array, the effect no longer makes a selection until it is in the tabs array.

This does leave a situation where initalTabName could be declared and the matching tab is never present, but I'd consider this implementor error (and the same issue could happen before #46471).

I have refactored the code a bit here too. I personally found the code a little hard to understand with the added logic, so it's now a little more verbose, but hopefully easier to follow.

Testing Instructions

1. Add a navigation block to a post and add some inner blocks to it
2. In the nav block's block inspector List View interface, select the 'Edit block' button of one of the inner blocks
3. Press the 'Go to parent' button at the top of the inspector panel when that inner block is selected.

Expected - the List View tab should be selected again on the navigation block.
In trunk - the Appearance tab is selected.

Screenshots or screencast

Before

Kapture.2023-01-12.at.14.18.34.mp4

After

Kapture.2023-01-12.at.14.16.22.mp4

[talldan]

The previous code didn't do so, but the component should probably consider a case where all tabs are disabled.

It might be handled elsewhere in the component though, I haven't really checked.

[github-actions]

Flaky tests detected in 9103fe2.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/3899933660
📝 Reported issues:

• [Flaky Test] results in two remaining blocks and positions the caret at the end of the second block #39805 in specs/editor/various/block-deletion.test.js

[scruffian]

LGTM

[ciampo]

Thank you both for flagging the issue and working on a fix so quickly 🙏