feat: create an RPC that returns the historical rewards for an earner

[seanmcgary]

For a given earner, return the rewards earned for each "snapshot", for each token where the amount for each snapshot entry is the amount earned since the last applicable snapshot, rather than the cumulative earned.

// GET /earners/{earnerAddress}/historical-rewards
{
	"rewards": [
		{
			"token": string,
			"amounts": [
				{
					"amount": string (bigint),
					"snapshot": string
			]
	]
}

Similarly, provide a route that can filter for a specific token

// GET /earners/{earnerAddress}/tokens/{tokenAddress}/historical-rewards
{
	"rewards": [
		{
			"token": string,
			"amounts": [
				{
					"amount": string (bigint),
					"snapshot": string
			]
	]
}