docs: README suggestions for clarity and formatting

[goshlanguage]

Motivation

This change improves the top-level README for the Cluster Validation Suite (CVS) by fixing typos, improving clarity, and modernizing formatting. No functional changes are included.

Key changes:

• Clarified several ambiguous sentences
• Reworded the introduction for better readability and accuracy
• Corrected the description of the -s pytest flag
• Standardized capitalization (Linux, pytest, burn-in, multi-node, etc.)
• Reorganized directory descriptions into a clearer table
• Updated examples to use consistent code blocks and ordering of arguments
• Simplified installation and environment setup sections

These changes make the README easier to follow for new users while retaining
all original content and structure.

Technical Details

Test Plan

Test Result

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.