Closes #2141

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

TODO:
- [ ] Address the TODOs in the code
- [ ] Manage what's gonna be the initially active message,
    because initially they're all active, so
    tabbing to the messages list from the top selects
    the first rendered one as the active one.
    #4292
    could help with this.
    This is also not great for performance: changing `tabindex`
    on a bunch of messages makes them all re-render.
    And otherwise, we probably want to update which one is
    the active one as new messages arrive.

Closes #2141

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

TODO:
- [ ] Address the TODOs in the code
- [ ] Manage what's gonna be the initially active message,
    because initially they're all active, so
    tabbing to the messages list from the top selects
    the first rendered one as the active one.
    #4292
    could help with this.
    This is also not great for performance: changing `tabindex`
    on a bunch of messages makes them all re-render.
    And otherwise, we probably want to update which one is
    the active one as new messages arrive.
- [ ] The interactive items with `onClick` must be actual semantic
    `<button>`s.
    See #4210
    for reference.

Closes #2141

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

TODO:
- [ ] Address the TODOs in the code
- [ ] Manage what's gonna be the initially active message,
    because initially they're all active, so
    tabbing to the messages list from the top selects
    the first rendered one as the active one.
    #4292
    could help with this.
    This is also not great for performance: changing `tabindex`
    on a bunch of messages makes them all re-render.
    And otherwise, we probably want to update which one is
    the active one as new messages arrive.
- [ ] The interactive items with `onClick` must be actual semantic
    `<button>`s.
    See #4210
    for reference.

Closes #2141

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

Closes #2141.

Basically what this commit comes down to:
1. Apply `useRovingTabindex` for message items
2. Set `tabindex="-1"` on all the interactive items
    inside every message that is currently not the active one,
    so that they do no have tab stops.

This appears to implement the Grid pattern:
https://www.w3.org/WAI/ARIA/apg/patterns/grid/.