Stake account should assert on lamport balance

[mcintyre94]

Currently the stake assertions only asserts on authorized withdrawer + staker:

lighthouse-assertion-builder/src/strategyBuilders/stakeProgram/account.ts

Lines 26 to 46 in 322cf12

	assertions.push({
	__kind: 'MetaAssertion',
	fields: [
	{
	__kind: 'AuthorizedWithdrawer',
	value: publicKey(simulatedAccount.state.meta.authorized.withdrawer),
	operator: EquatableOperator.Equal,
	},
	],
	});
	assertions.push({
	__kind: 'MetaAssertion',
	fields: [
	{
	__kind: 'AuthorizedStaker',
	value: publicKey(simulatedAccount.state.meta.authorized.staker),
	operator: EquatableOperator.Equal,
	},
	],
	});

IMO there should also be an assertion on the lamport balance of the stake account (using AssertAccountInfo) to ensure there's not an unexpected withdrawal/expected deposit that doesn't happen.