feat(solana-client): Support SOLANA_METRICS_CONFIG env variable (#2048)

[0xcypher02]

This PR attempts to resolve #2048 by allowing operators to set a metrics.solana_metrics_config configuration option which will properly set the SOLANA_METRICS_CONFIG environment variable when spawning the Solana Client.

Please let me know if the base branch should be changed. I know main is for firedrancer and not frankendancer, so opted to use the v0.1 branch as base.