getInflation RPC endpoint is less useful than it could be

[mvines]

The getInflation RPC endpoint blindly returns:

solana/sdk/src/inflation.rs

Lines 5 to 23 in 58ef02f

	pub struct Inflation {
	/// Initial inflation percentage, from time=0
	pub initial: f64,
	/// Terminal inflation percentage, to time=INF
	pub terminal: f64,
	/// Rate per year, at which inflation is lowered until reaching terminal
	/// i.e. inflation(year) == MAX(terminal, initial*((1-taper)^year))
	pub taper: f64,
	/// Percentage of total inflation allocated to the foundation
	pub foundation: f64,
	/// Duration of foundation pool inflation, in years
	pub foundation_term: f64,
	/// Percentage of total inflation allocated to storage rewards
	pub storage: f64,
	}

thus forcing the client to implement methods like:

solana/sdk/src/inflation.rs

Lines 68 to 70 in 58ef02f

	pub fn validator(&self, year: f64) -> f64 {
	self.total(year) - self.storage(year) - self.foundation(year)
	}

Suggestion:

1. Obsolete the getInflation endpoint
2. Add a getInflationGovernor endpoint(like https://docs.solana.com/apps/jsonrpc-api#getfeerategovernor) that returns the current getInflation data (minus the .storage field, cc: Deal with misleading storage rewards in Inflation struct #10092)
3. Add getInflationRate endpoint that returns the actual rate of inflation (total/validator/foundation) for the given epoch (or the current epoch if unspecified)