rpc_api.md: account for previous RPC API updates

Summary

• rpc_api.md: account for previous RPC API updates
• rpc_api.md: proofread and edit

Address description changes from:

• .proc_apply_schema_change — picodata!1218 (merged) (24.5.0-310)
• .proc_runtime_info:
  • add slab_info — picodata!1253 (merged) (24.6.0-17)
  • add governor_step_counter — picodata!1325 (merged) (24.7.0-12)
• .proc_sharding_bootstrap — picodata!1138 (merged) (24.6.0-74)

picodata 24.7.0-50-g8ee03d19

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• Close nothing
• Cherry-pick to: partially
• Staging: https://docs.binary.picodata.io/picodata/asabirov_previous_rpc_api_updates/architecture/rpc_api/