Add ROCm 6.2 VRAM optimization for AMD GPUs (8-16GB)

[darkjive]

This commit adds comprehensive ROCm 6.2 support and VRAM optimization for AMD GPUs, specifically targeting systems with 8-16GB VRAM.

Changes:

• Updated webui.sh to use ROCm 6.2 instead of 5.7 for AMD GPUs

• Added webui-user-rocm62.sh: Optimized launch script with:

  • PyTorch ROCm 6.2 installation command
  • PYTORCH_HIP_ALLOC_CONF for memory fragmentation prevention
  • Optimized command-line flags (--medvram, --opt-split-attention, etc.)
  • Detailed inline documentation

• Added ROCM_VRAM_OPTIMIZATION.md: Comprehensive 400+ line guide covering:

  • Launch configuration and environment variables
  • WebUI settings optimization
  • Generation settings for different VRAM amounts
  • ControlNet optimization techniques
  • Recommended workflows for quality and performance
  • Extensive troubleshooting section
  • Performance benchmarks

• Added README_ROCM.md: Quick start guide for ROCm setup

Key optimizations:

• Memory fragmentation prevention via expandable_segments
• Optimal command-line arguments for 16GB VRAM
• Two-phase workflow (generate at 512x512, upscale separately)
• ControlNet low VRAM mode configuration
• Batch processing best practices

Benefits:

• Prevents OOM errors on 16GB VRAM GPUs
• Improved stability for long generation sessions
• Better quality outputs through optimized workflows
• Faster iteration with recommended settings

Description

• a simple description of what you're trying to accomplish
• a summary of changes in code
• which issues it fixes, if any

Screenshots/videos:

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests