Support multiple external IPs in blueprint zone type - #11236

control: job assigned to worker 01M1Y31T7DPDHG44RA24WWSM6Y [factory aws, i-03a88cc9907357f13] (queued for 44 s)
...
task: starting task 0: "setup"
task: process exited: duration 4085 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 16371 ms, exit code 0
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task: starting task 2: "authentication"
task: process exited: duration 16 ms, exit code 0
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task: starting task 3: "clone repository"
task: process exited: duration 14204 ms, exit code 0
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task: starting task 4: "build"
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| info: running `cargo check --bins` on zone-setup (376/376)
| warning: profile package spec `blake2b_simd` in profile `dev` did not match any packages
| warning: profile package spec `rust-argon2` in profile `dev` did not match any packages
|     Checking uzers v0.12.2
|     Checking zone-setup v0.1.0 (/work/oxidecomputer/omicron/zone-setup)
|     Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.75s
| 
| real    14:24.555486037
| user    21:33.734543764
| sys      4:23.828904964
| trap        0.338143181
| tflt        0.584392316
| dflt        0.853688266
| kflt        0.004776610
| lock  1:31:10.012282719
| slp   1:42:59.083137498
| lat        57.588496791
| stop     4:06.363697939
task: process exited: duration 996608 ms, exit code 0
|W| found 0 output files