feat: model remove cmd

[reidliu41]

What does this PR do?

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

add a subcommand, help to clean the unneeded model:

$ llama model --help
usage: llama model [-h] {download,list,prompt-format,describe,verify-download,remove} ...

Work with llama models

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

$ llama model remove --help
usage: llama model remove [-h] -m MODEL [-f]

Remove the downloaded llama model

options:
  -h, --help            show this help message and exit
  -m MODEL, --model MODEL
                        Specify the llama downloaded model name
  -f, --force           Used to forcefully remove the llama model from the storage without further confirmation

$ llama model remove -m Llama3.2-1B-Instruct:int4-qlora-eo8
Are you sure you want to remove Llama3.2-1B-Instruct:int4-qlora-eo8? (y/n): n
Removal aborted.

$ llama model remove -mLlama3.2-1B-Instruct:int4-qlora-eo8-f
Llama3.2-1B-Instruct:int4-qlora-eo8 removed.

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.]

[ashwinb]

you don't need this function at all. you can simply change this to say:

if input("....").lower() == "y":

at the callsite

[ashwinb]

before asking for confirmation or doing anything you should check if the model is legitimate and if the directory even exists or not