`Test_ProxyServer_Headers` never passed `--http-address`, so it bound to
the default `127.0.0.1:3000`.
`TestWorkspaceProxy_Server_PrometheusEnabled`
used `RandomPort(t)` for `--http-address` (a drive-by from #14972 which
was
fixing the Prometheus port).
Both now use `--http-address :0`. `ConfigureHTTPServers` calls
`net.Listen("tcp", ":0")` and holds the listener open, so there is no
TOCTOU window. Neither test connects to the HTTP listener, so the
assigned port is irrelevant. This matches `cli/server_test.go` where
`:0` is used throughout.
This PR makes the initial steps at removing usage of the global Go HTTP
client, which was seen to have impacts on test flakiness in
https://github.com/coder/internal/issues/1020. The first commit removes
uses from tests, with the exception of one test that is tightly coupled
to the default client. The second commit makes easy/low-risk removals
from application code. This should have some impact to reduce test flakiness.
Mathias Fredriksson