core/state, tests: fix memory leak via fastcache

[holiman]

This change fixes a memory leak, when running either state-tests or blockchain-tests, we allocate a 1MB fastcache during snapshot generation. fastcache is a bit special, and requires a Reset() (it has it's own memory allocator).

The 1MB was hidden here and here respectively.

EDIT:

This PR also disables the long-running tests on windows/appveyor, by using the -short flag to tests. This disables the following statetests:

	st.slow(`^stAttackTest/ContractCreationSpam`)
	st.slow(`^stBadOpcode/badOpcodes`)
	st.slow(`^stPreCompiledContracts/modexp`)
	st.slow(`^stQuadraticComplexityTest/`)
	st.slow(`^stStaticCall/static_Call50000`)
	st.slow(`^stStaticCall/static_Return50000`)
	st.slow(`^stSystemOperationsTest/CallRecursiveBomb`)
	st.slow(`^stTransactionTest/Opcodes_TransactionInit`)

And these blockchain tests:

	// Slow tests
	bt.slow(`.*bcExploitTest/DelegateCallSpam.json`)
	bt.slow(`.*bcExploitTest/ShanghaiLove.json`)
	bt.slow(`.*bcExploitTest/SuicideIssue.json`)
	bt.slow(`.*/bcForkStressTest/`)
	bt.slow(`.*/bcGasPricerTest/RPC_API_Test.json`)
	bt.slow(`.*/bcWalletTest/`)

[MariusVanDerWijden]

LGTM

[holiman]

Interesting!
It passed on appveyor/ubuntu, but window/386

ok  	github.com/ethereum/go-ethereum/eth/gasprice	1.040s
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x0 pc=0x78d247]
goroutine 34 [running]:
github.com/VictoriaMetrics/fastcache.(*Cache).HasGet(0x0, {0x0, 0x0, 0x0}, {0xadef7e4, 0x20, 0x20})
	C:/Users/appveyor/go/pkg/mod/github.com/!victoria!metrics/fastcache@v1.12.1/fastcache.go:174 +0x37
github.com/ethereum/go-ethereum/core/state/snapshot.(*diskLayer).AccountRLP(0xaf47aa0, {0x0, 0xbf, 0x49, 0xf4, 0x40, 0xa1, 0xcd, 0x5, 0x27, ...})
	C:/projects/go-ethereum/core/state/snapshot/disklayer.go:115 +0x197
github.com/ethereum/go-ethereum/core/state/snapshot.(*diskLayer).Account(0xaf47aa0, {0x0, 0xbf, 0x49, 0xf4, 0x40, 0xa1, 0xcd, 0x5, 0x27, ...})
	C:/projects/go-ethereum/core/state/snapshot/disklayer.go:81 +0x30
github.com/ethereum/go-ethereum/core/state.(*StateDB).getDeletedStateObject(0xaf6a280, {0x71, 0x56, 0x2b, 0x71, 0x99, 0x98, 0x73, 0xdb, 0x5b, ...})
	C:/projects/go-ethereum/core/state/statedb.go:569 +0x10d
github.com/ethereum/go-ethereum/core/state.(*StateDB).getStateObject(...)
	C:/projects/go-ethereum/core/state/statedb.go:550
github.com/ethereum/go-ethereum/core/state.(*StateDB).GetNonce(0xaf6a280, {0x71, 0x56, 0x2b, 0x71, 0x99, 0x98, 0x73, 0xdb, 0x5b, ...})
	C:/projects/go-ethereum/core/state/statedb.go:293 +0x39
github.com/ethereum/go-ethereum/core.(*StateTransition).preCheck(0xadefda0)
	C:/projects/go-ethereum/core/state_transition.go:272 +0x81
github.com/ethereum/go-ethereum/core.(*StateTransition).TransitionDb(0xadefda0)
	C:/projects/go-ethereum/core/state_transition.go:363 +0x62
github.com/ethereum/go-ethereum/core.ApplyMessage(0xaf123c0, 0xaccdb90, 0xacb35d8)
	C:/projects/go-ethereum/core/state_transition.go:181 +0x50
github.com/ethereum/go-ethereum/core.precacheTransaction(0xaccdb90, 0x1348a20, 0xacb35d8, 0xaf6a280, 0xaf6e240, 0xaf123c0)
	C:/projects/go-ethereum/core/state_prefetcher.go:92 +0x20c
github.com/ethereum/go-ethereum/core.(*statePrefetcher).Prefetch(0xac8f7d0, 0xaf523c0, 0xaf6a280, {{0x0, 0x0}, 0x0, 0x0, {0x0, 0x0, 0x0}}, ...)
	C:/projects/go-ethereum/core/state_prefetcher.go:71 +0x55c
github.com/ethereum/go-ethereum/core.(*BlockChain).insertChain.func3({0xc144ad210a62ad18, 0x4027a85, 0x1348860}, 0xaf523c0, 0xaf6a280)
	C:/projects/go-ethereum/core/blockchain.go:1799 +0x73
created by github.com/ethereum/go-ethereum/core.(*BlockChain).insertChain in goroutine 24
	C:/projects/go-ethereum/core/blockchain.go:1798 +0x258a
FAIL	github.com/ethereum/go-ethereum/eth/protocols/eth	0.154s

Ah, the precacher is using the same snap structure, and we niled the cache