EIP3322 - Account gas storage opcodes

# Simple Summary

Allows contract accounts to store gas that can be transferred to the refund counter.

# Abstract

Contracts can persist gas for later transfer to the refund counter. Three opcodes are introduced to read, add to, and use this gas counter.

# Motivation

The refund mechanism is currently being used by gas tokens to arbitrage gas price. This brings gas supply elasticity and price stability by moving gas from blocks with less demand to blocks with more demand. Unfortunately this rewards unnecessary state growth. By introducing a superior gas storage mechanism, the gas market will require less storage and computation.

# Specification

Contract accounts gain an unsigned gas refund counter, initially zero.

Three new opcodes are introduced to manage this state.

SELFGAS (0x49): Pushes the current account's gas refund counter onto the stack. Shares gas pricing with SELFBALANCE.
USEGAS (0x4a): Pops amount from the stack. The minimum of amount and the current account's gas refund counter is transferred to the execution context's refund counter. Costs 5000 gas.
STOREGAS (0x4b): Pops amount from the stack. Costs 5000 + amount gas. Increases the current account's gas refund counter by amount.

# Rationale

By reusing the execution context's refund counter we can reuse its 50% DoS protection, which limits its block elasticity contribution to 2x.

The gas costs are based on similar opcodes SELFBALANCE and SSTORE.

Most accounts will store no gas, so the per-account storage overhead should be minimal or even zero in the normal case.

The opcode numbers chosen are in the same 0x4X range as SELFBALANCE and GASLIMIT.

# Backwards Compatibility

Because the gas is added to the refund counter, no compatibility issues are anticipated.

# Test Cases

Code	Used Gas	Refund	Original	Final
0x60004900	5003	0	0	0
0x60034900	5003	2	2	0
0x60034900	5003	3	3	0
0x60034900	5003	3	4	1
0x60034960034900	10006	4	4	0
0x60034960034900	10006	6	6	0
0x484900	5010	100000	100000	0
0x61ffff4a00	70538	0	0	65535

# Security Considerations

DoS is already limited by the 50% refund limit.