Removes command_line from core

[nerdai]

Description

• Part 2 of effort to remove core from CLI
• Part 1, we prepared the llama-index-cli package
• In this part, we remove command line from llama-index-core
• NOTE: I've kept command_line/mappings.json as our download modules depends on this file to determine the package name for a class name (of a pack/tool/reader).
• TODO in this PR:
  • build/publish new version of core with cli removed
  • update llama-index starter deps to update range of llama-index-core dep to ensure it uses versions with cli removed
  • update llama-index starter deps to include llama-index-cli package
  • update docs where we make mention of cli existing in core package

Type of Change

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• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• I stared at the code and made sure it makes sense