errors from Clickhouse test setup failure could be more explicit

[davepacheco]

@plotnick saw a test failure that looked similar to this:

$ cargo test -p omicron-nexus --test=test_all -- integration_tests::unauthorized
    Finished test [unoptimized + debuginfo] target(s) in 0.57s
     Running tests/test_all.rs (target/debug/deps/test_all-cfbe7e181ced3561)

running 2 tests
test integration_tests::unauthorized_coverage::test_unauthorized_coverage ... ok
test integration_tests::unauthorized::test_unauthorized ... FAILED

failures:

---- integration_tests::unauthorized::test_unauthorized stdout ----
log file: "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/test_all-cfbe7e181ced3561-test_unauthorized.52946.0.log"
note: configured to log to "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/test_all-cfbe7e181ced3561-test_unauthorized.52946.0.log"
thread 'integration_tests::unauthorized::test_unauthorized' panicked at 'called `Result::unwrap()` on an `Err` value: No such file or directory (os error 2)', /Users/dap/oxide/omicron/nexus/test-utils/src/lib.rs:99:72
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
WARN: dropped CockroachInstance without cleaning it up first (there may still be a child process running and a temporary directory leaked)
WARN: temporary directory leaked: /var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/.tmplhhJGt


failures:
    integration_tests::unauthorized::test_unauthorized

test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 67 filtered out; finished in 0.81s

error: test failed, to rerun pass '-p omicron-nexus --test test_all'

I'm not sure what the failure mode in his case was, but I reproduced it by just not having clickhouse on my PATH. This change adds context to a bunch of error paths in the function that was failing. Now for my failure mode I see this:

$ cargo test -p omicron-nexus --test=test_all -- integration_tests::unauthorized
    Blocking waiting for file lock on build directory
   Compiling omicron-test-utils v0.1.0 (/Users/dap/oxide/omicron/test-utils)
   Compiling nexus-test-utils v0.1.0 (/Users/dap/oxide/omicron/nexus/test-utils)
   Compiling omicron-nexus v0.1.0 (/Users/dap/oxide/omicron/nexus)
    Finished test [unoptimized + debuginfo] target(s) in 1m 40s
     Running tests/test_all.rs (target/debug/deps/test_all-cfbe7e181ced3561)

running 2 tests
test integration_tests::unauthorized_coverage::test_unauthorized_coverage ... ok
test integration_tests::unauthorized::test_unauthorized ... FAILED

failures:

---- integration_tests::unauthorized::test_unauthorized stdout ----
log file: "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/test_all-cfbe7e181ced3561-test_unauthorized.53138.0.log"
note: configured to log to "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/test_all-cfbe7e181ced3561-test_unauthorized.53138.0.log"
thread 'integration_tests::unauthorized::test_unauthorized' panicked at 'called `Result::unwrap()` on an `Err` value: failed to spawn `clickhouse` (with args: ["server", "--log-file", "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/.tmpwfZdb1/clickhouse-server.log", "--errorlog-file", "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/.tmpwfZdb1/clickhouse-server.errlog", "--", "--http_port", "0", "--path", "/var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/.tmpwfZdb1"])

Caused by:
    No such file or directory (os error 2)', /Users/dap/oxide/omicron/nexus/test-utils/src/lib.rs:99:72
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
WARN: dropped CockroachInstance without cleaning it up first (there may still be a child process running and a temporary directory leaked)
WARN: temporary directory leaked: /var/folders/x3/6tbrhnss6zz677z4zjsyvkqc0000gn/T/.tmp78KfQx


failures:
    integration_tests::unauthorized::test_unauthorized

test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 67 filtered out; finished in 1.09s

error: test failed, to rerun pass '-p omicron-nexus --test test_all'

so instead of just saying "No such file or directory", it says that it got this error while spawning clickhouse.

[davepacheco]

@plotnick confirmed the spawn failure is the case he saw, so this should indeed cover that.