fix: optimize and re-format usage message

[vladdoster]

Description

• fix zinit --help
• format available ices and move to ice command usage.
• check for -h|--help|help first instead of last
• add --help to ice command
• update zinit usage message
• remove deprecated commands (e.g., list, clist, ls)

Related Issue(s)

N/A

Motivation and Context

Usage examples

before

after

How Has This Been Tested?

Types of changes

• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] Documentation change
• [X] New feature (non-breaking change which adds functionality)

Checklist:

• [X] All new and existing tests passed.
• [X] I have added tests to cover my changes.
• [X] I have updated the documentation accordingly.

[vladdoster]

Current format is on the left and new on right.