We need to add support of Valkey execution on pmm-agent side.

For that we need to do following:

• Update pmm-agent ↔︎ pmm-managed communication API

• Add ability to configure path to valkey_exporter

• Add ability to run valkey_exporter by pmm-agent

• Prepare configuration to run Valkey on pmm-managed side

• check for pmm-agent version to run valkey exporter