feat: default to Ethereum network in ProviderBuilder

[DaniPopes]

Ref #263

[DaniPopes]

need to be careful here not to ignore N, previously this would reset it back to ()

[prestwich]

maybe add pub fn network<Other: Network>(self) -> ProviderBuilder<Stack<Inner, L>, Other> for lazy users or programmatic switching?

[DaniPopes]

Already exists

alloy/crates/provider/src/builder.rs

Lines 114 to 125 in 9a33128

	/// Change the network.
	///
	/// By default, the network is invalid, and contains the unit type `()`.
	/// This method MUST be called before the provider is built. The `client`
	/// and `provider` methods only exist when the network is valid.
	///
	/// ```rust,ignore
	/// builder.network::<Arbitrum>()
	/// ```
	pub fn network<Net: Network>(self) -> ProviderBuilder<L, Net> {
	ProviderBuilder { layer: self.layer, network: PhantomData }
	}

[DaniPopes]

Just noticed docs need an update. cc @onbjerg we want Ethereum here by default right?

[prestwich]

yes Ethereum by default