feat: add show environment infomation subcmd

[reidliu41]

What does this PR do?

[Provide a short summary of what this PR does and why. Link to relevant issues if applicable.]

As a llama stack server side, it would be better to have a utility to show some environment information:

• quickly get info we need, and help to troubleshoot
• we can customize what information we need to check

$ llama
usage: llama [-h] {model,stack,download,verify-download,info} ...

Welcome to the Llama CLI

options:
  -h, --help            show this help message and exit

subcommands:
  {model,stack,download,verify-download,info}

  model                 Work with llama models
  stack                 Operations for the Llama Stack / Distributions
  download              Download a model from llama.meta.com or Hugging Face Hub
  verify-download       Verify integrity of downloaded model files
  info                  Show llama stack environment information

e.g.
$ llama info
system:
  sys.version: 3.10.16 (main, Dec 11 2024, 10:22:29) [Clang 14.0.6 ]
  sys.platform: darwin
  platform.machine: arm64
  platform.node: xxx
  platform.python_version: 3.10.16
  platform.cpu_brand: Apple M3 Pro
  memory.used: 18.06 GB
  memory.available: 17.12 GB
  memory.total: 36.00 GB

llama packages:
  llama_models.version: 0.1.4
  llama_stack.version: 0.1.4
  llama_stack_client.version: 0.1.4

torch packages:
  torch.version: 2.6.0
  torchao.version: 0.8.0
  torchtune.version: 0.5.0
  torchvision.version: 0.21.0

Test Plan

[Describe the tests you ran to verify your changes with result summaries. Provide clear instructions so the plan can be easily re-executed.]