feat(cli): rhc collector CLI

[pkoprda]

• Card ID: CCT-1845

Add comprehensive collector CLI interface with commands:

• rhc collector info - Display collector information
• rhc collector list - List available collectors
• rhc collector timers - List collector timers
• rhc collector enable [--now] - Enable timer-based collection
• rhc collector disable [--now] - Disable timer-based collection

An example of how to test this PR:

# systemctl enable rhc-server.socket rhc-server.service
# systemctl start rhc-server.socket rhc-server.service
# mkdir -p /usr/lib/rhc/collectors/
# cat /usr/lib/rhc/collectors/com.redhat.advisor.toml
[meta]
name = "Red Hat Lightspeed Advisor"
feature = "analytics"
type = "ingress"

[ingress]
user = "root"
group = "root"
content_type = "application/vnd.redhat.advisor.collection"
# mkdir -p /var/cache/rhc/collectors/
# cat /var/cache/rhc/collectors/com.redhat.advisor.json
{
  "last_started": {"timestamp": 1777461050},
  "last_finished": {"timestamp": 1777461150, "exit_code": 0}
}

# rhc collector
NAME:
   rhc collector - Collect data for analysis

USAGE:
   rhc collector COMMAND [command options]

COMMANDS:
   info     Display collector information
   list     List available collectors
   timers   List collector timers
   enable   Enable timer-based collection
   disable  Disable timer-based collection
   help, h  Shows a list of commands or help for one command

OPTIONS:
   --help, -h  show help
# rhc collector list
ID                  NAME
com.redhat.advisor  Red Hat Lightspeed Advisor
# rhc collector info com.redhat.advisor
Name:      Red Hat Lightspeed Advisor
Feature:   analytics

Last run:  Wed 2026-04-29 07:12 EDT (2h 48m ago)
Next run:  -

Config:   /usr/lib/rhc/collectors/com.redhat.advisor.toml
Service:  rhc-collector-com.redhat.advisor.service
Timer:    rhc-collector-com.redhat.advisor.timer
# rhc collector timers
ID                  LAST    NEXT
com.redhat.advisor  2h 48m  -

Hint: Run 'rhc collector info COLLECTOR' to show more details.

[m-horky]

I have not discovered any significant issues, overall the code feels solid and considering the state of the codebase well structured.

UX notes:

• With no data collector, list outputs failed to list collectors: EOF. Could we display some better message, like "Error: No data collectors are available"?
• rhc collector timers does not display the value of NEXT, even when the timer is enabled. It may be because we aren't passing --all flag to systemctl list-timers.

More inline.

[m-horky]

Nothing stands out, you have my ACK. I'm leaving the resolution of the rest of my comments up to you.

[mjcr99]

Thanks for the PR @pkoprda! LGTM, I have a nit suggestion.

[mjcr99]

LGTM