[omdb] refactor attached_subnet_manager status into a Display and snapshot it - #11552

control: job assigned to worker 01M5JDAKJRPBVB32MAWA87MVGB [factory aws, i-0b1958020d601e769] (queued for 53 s)
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task: starting task 0: "setup"
task: process exited: duration 4096 ms, exit code 0
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task: starting task 1: "rust-toolchain"
task: process exited: duration 17017 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 20734 ms, exit code 0
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task: starting task 4: "build"
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|    Compiling omicron-generation-kinds v0.1.0 (/work/oxidecomputer/omicron/generation-kinds [...]
|    Compiling serde_with v3.21.0
|    Compiling omicron-ledger v0.1.0 (/work/oxidecomputer/omicron/ledger)
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|    Compiling tufaceous-artifact v0.2.0 (https://github.com/oxidecomputer/tufaceous?branch= [...]
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|    Compiling omicron-common v0.1.0 (/work/oxidecomputer/omicron/common)
|    Compiling test-project v0.1.0 (/tmp/test-project)
|     Finished `release` profile [optimized] target(s) in 1m 02s
task: process exited: duration 100020 ms, exit code 0
|W| found 0 output files