feat: add CPU limit multiplier to simple limit strategy

[patsevanton]

This PR introduces a new configuration parameter cpu_limit_multiplier to the SimpleLimitStrategy, providing more flexible control over CPU limit recommendations.

Changes:

• Added cpu_limit_multiplier field to SimpleLimitStrategySettings with default value of 1.0
• Updated CPU limit calculation to multiply the percentile-based value by the multiplier
• Modified strategy description to reflect the new multiplier in the output format
• Updated example command in description to include the new parameter

Benefits:

• Allows users to set CPU limits as a percentage of the calculated percentile (e.g., 200% of 96th percentile)
• Provides more granular control over resource allocation strategies
• Maintains backward compatibility with default multiplier of 1.0
• Useful for workloads that need headroom above statistical percentiles

Example Usage:

krr simple_limit --cpu_limit_multiplier=2.0  # Sets limit to 200% of percentile
krr simple_limit --cpu_limit_multiplier=1.5  # Sets limit to 150% of percentile