[profilecli] Add ready command

[bryanhuhta]

When doing some local testing, I came across the problem where I wanted to quickly check if pyroscope was up. A similar problem was described here #3468 and @korniltsev commented a similar solution #3468 (comment).

$ profilecli ready --help
usage: profilecli ready [<flags>]

Check Pyroscope health.

Flags:
  -h, --help              Show context-sensitive help (also try --help-long and --help-man).
      --version           Show application version.
  -v, --verbose           Enable verbose logging.
      --url="http://localhost:4040"  
                          URL of the profile store.
      --tenant-id=""      The tenant ID to be used for the X-Scope-OrgID header.
      --username=""       The username to be used for basic auth.
      --password=""       The password to be used for basic auth.
      --protocol=connect  The protocol to be used for communicating with the server.

Using profilecli ready will hit the /ready health check endpoint. Examples:

# Local server not accepting traffic
$ profilecli ready
error: Get "http://localhost:4040/ready": dial tcp [::1]:4040: connect: connection refused

# Local server accepting traffic but not ready
$ profilecli ready
level=error msg="not ready" status="503 Service Unavailable" body="Ingester not ready: waiting for 15s after being ready\n"

# Local server accepting traffic and ready
$ profilecli ready
level=info msg=ready

# Remote server accepting traffic but not ready
$ profilecli ready --url "https://firedev001.grafana-dev.net" --username 1218 --password "<redacted>"
level=error msg="not ready" status="503 Service Unavailable" body="{\"code\":\"Loading\",\"message\":\"Your instance is loading, and will be ready shortly.\"}\n"

# Remote server accepting traffic and ready
$ profilecli ready --url "https://firedev001.grafana-dev.net" --username 1218 --password "<redacted>"
level=info msg=ready

[korniltsev]

nice

[simonswine]

LGTM