Fix organizations data tree in org page

[fyliu]

Fixes

• Reparented orgs that should be outside "Code for All". They are now under siblings of "Code for All"
• Converted hard-coded "Code for All" dropdown to list grandparent orgs
• Converted grandparent org dropdown to use Dropdown component
• Fixed the issue where closing an inner Dropdown list will close the top level dropdown as well
• Tracked parent expanded beyond 6 orgs with component state rather than inside org-tree structure
• Fixed org counts to exclude all parent orgs
• Fixed loading indicator logic
• Updated tests

Suggested future work

• Loading indicator may not be fully working still. I fixed the reversed logic, but didn't try to test it.
• Index contributor indicator icon placement might need to be fixed. Currently, they're shown next to the granparent and parent orgs and not next to the index contributor orgs.
• The way the sub-orgs are counted might need to be fixed. I added code to exclude grandparent and parent orgs from the count. This is to "fix" the discrepancy between the index contributor count saying 8 orgs and the Code for All gp org displaying a count of 9 orgs. It's easy to revert to counting parent and grandparent orgs from here.
• Unaffiliated orgs list might be able to reuse the internals of the Dropdown component. Affiliate orgs is using Dropdown, so it's more consistent if unaffiliate orgs is using the same code.

Closes #1238

[codeclimate[bot]]

Code Climate has analyzed commit 6aefb168 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 98.5% (50% is the threshold).

This pull request will bring the total coverage in the repository to 81.0% (0.2% change).

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