Enable RPC limiters for some providers

[friofry]

It requires refactoring the existing Network type and excluding RPC providers to a separate table.

// RpcProviderAuthType defines the different types of authentication for RPC providers
type RpcProviderAuthType int

const (
	NoAuth RpcProviderAuthType = iota // No authentication
	// Example: Used for public nodes or local nodes without any authentication.
	// Example: "http://localhost:8545"

	BasicAuth // Authentication via Basic Auth
	// Example: Uses a username and password encoded as a base64 string and passed in the request header.
	// Example: Header "Authorization: Basic base64(username:password)", URL: "https://api.example.com"

	URLPathAuth // Authentication via token in URL path
	// Example: The token is included directly in the URL path.
	// Example: "https://api.example.com/YOUR_TOKEN"
)

// RpcProvider represents an RPC provider configuration with various options
type RpcProvider struct {
	ChainID          uint64 `json:"chainId"`          // Chain ID of the network
	Name             string `json:"name"`             // Provider name for identification
	URL              string `json:"url"`              // Current Provider URL (may include overrides)
	OriginalURL      string `json:"originalUrl"`      // Original URL before any overrides
	EnableRPSLimiter bool   `json:"enableRpsLimiter"` // Enable RPC rate limiting for this provider
}

type Network struct {
	ChainID                uint64          `json:"chainId"`
	ChainName              string          `json:"chainName"`
	RpcProviders           []RpcProvider   `json:"rpcProviders"` // List of RPC providers, in the order in which they are accessed
	BlockExplorerURL       string          `json:"blockExplorerUrl,omitempty"`
	IconURL                string          `json:"iconUrl,omitempty"`
	NativeCurrencyName     string          `json:"nativeCurrencyName,omitempty"`
	NativeCurrencySymbol   string          `json:"nativeCurrencySymbol,omitempty"`
	NativeCurrencyDecimals uint64          `json:"nativeCurrencyDecimals"`
	IsTest                 bool            `json:"isTest"`
	Layer                  uint64          `json:"layer"`
	Enabled                bool            `json:"enabled"`
	ChainColor             string          `json:"chainColor"`
	ShortName              string          `json:"shortName"`
	TokenOverrides         []TokenOverride `json:"tokenOverrides"`
	RelatedChainID         uint64          `json:"relatedChainId"`
}

as discussed here: #5941 (comment)