[Doc] Documentation Updates

[anmolagarwalcp810]

Changes made:

1. Shortened run_benchmark command.
2. Added plots to capacity search, how to use metron and prefill profiling pages.
3. Move metrics section to index toctree so that its visible at the top.
4. Updated figures on visualizing metrics page.
5. Replaced "Getting Started" with "How to us metron"
6. Added link to documentation in README with a banner.
7. Added initial logo for metron on the banner.
8. Added html_context object to support backlink on ReadTheDocs.
9. Removed duplicate license inside docs and renamed LICENSE.txt to LICENSE inside main folder.
10. Changed default values for CLI args inside run_benchmark.py:
    • --should-use-given-dir now defaults to True
    • --should-write-metrics now defaults to False to prevent writing metrics to wandb by default. Helpful for users who may not have setup wandb.
11. Updated definition of fluidity index with target prefill and decode latencies instead of TTFT/TBT SLOs.
12. Added fluid-token-generation-rate metric.