Add tabs to access pages

[charliepark]

This PR splits the Silo Access and Project Access pages into tabs, so a viewer can see the roles broken down, showing just Users, just Groups, or All with access (and their respective roles). This also updates the forms on each tab's page, to show just "Add user", "Add group", or "Add user or group", depending on what tab it's shown on.

This is part of #2887, and will be useful for more detailed views of group member counts, user time_modified values (as in oxidecomputer/omicron#9494), more comprehensive lists of users, etc. I wanted to get these changes in first, though, to keep future PRs tighter.

The forms are slightly modified to make them more contextually-relevant as well. (Ignore the weird scaling difference due to the screenshot dimensions.)

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Project	Deployment	Review	Updated (UTC)
console	Ready	Preview	Dec 19, 2025 8:36pm

[charliepark]

I wonder if, since we show GROUPS higher on the ALL list than USERS, if we should order the tabs as ALL | GROUPS | USERS

[charliepark]

Here's the modal that shows the list of group members:

[charliepark]

I backed out the change to show the modal and the members of the group, as well as the members count column, until we have the updated API with the members count in it, so we can lazy-load the members list and avoid an n+1 on the table.