ui: Fix server list leader determination for IPv6

[backspace]

This closes #10513, thanks to @bastelfreak for the report.
GET /status/leader returns an IPv6 host with square brackets
around the IP address as expected, but the rpcAddr property
on the agent model does not.

This fixes rpcAddr, updates the Mirage /status/leader mock
to properly format an IPv6 host, and changes the agent
factory to sometimes produce IPv6 addresses.

I added a formatHost utility function to centralise the
conditional square bracket-wrapping that would have
otherwise been further scattered around.

[github-actions]

Ember Asset Size action

As of 1dadfc2

Files that got Bigger 🚨:

File	raw	gzip
nomad-ui.js	+245 B	+32 B

Files that stayed the same size 🤷‍:

File	raw	gzip
vendor.js	0 B	0 B
nomad-ui.css	0 B	0 B
vendor.css	0 B	0 B

[github-actions]

Ember Test Audit comparison

	main	1dadfc2	change
passes	1079	1079	0
failures	0	0	0
flaky	0	0	0
duration	8m 45s 184ms	8m 03s 069ms	-42s 115ms

[DingoEatingFuzz]

Wow, a rare bug that's as old as the UI!

The formatHost util is great for tucking away this tiny bit of complexity.

[bastelfreak]

@DingoEatingFuzz thanks for the merge and @backspace thanks for fixing it. Do you already know when the next release is plannend / are nightly binarys available with the fix?

[backspace]

It didn’t make it into 1.1.0, sadly, so it’ll have to wait for 1.1.1, which is currently unscheduled. There aren’t nightlies 😞

[github-actions]

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