node: Add BatchQueueSize metric

[palango]

Description

Adds a new metric batch_queue_size to op-node.
This is useful especially when using AltDA to monitor the nodes progress.

[tynes]

/ci auth a21bc0f

[tynes]

Looks like a nil pointer deref

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x58 pc=0xdd239d]

goroutine 1 [running]:
github.com/ethereum-optimism/optimism/op-node/rollup/derive.(*BatchQueue).Reset(0xc0001ce0e0?, {0xc00071e920?, 0xdddb79?}, {{0x6b, 0x7f, 0xde, 0x49, 0xe6, 0xba, 0x10, ...}, ...}, ...)
        /root/project/op-node/rollup/derive/batch_queue.go:269 +0x11d
github.com/ethereum-optimism/optimism/op-node/rollup/derive.(*BatchMux).Reset(0xc0005343c0, {0x1d43ca8, 0x26134e0}, {{0x6b, 0x7f, 0xde, 0x49, 0xe6, 0xba, 0x10, ...}, ...}, ...)
        /root/project/op-node/rollup/derive/batch_mux.go:48 +0x475
github.com/ethereum-optimism/optimism/op-node/rollup/derive.(*DerivationPipeline).Step(0xc00012c000, {0x1d43ca8, 0x26134e0}, {{0x9e, 0xbb, 0x4f, 0x94, 0x22, 0x14, 0x55, ...}, ...})
        /root/project/op-node/rollup/derive/pipeline.go:193 +0x3d2
github.com/ethereum-optimism/optimism/op-node/rollup/derive.(*PipelineDeriver).OnEvent(0xc0002bf7d0, {0x1d3b260?, 0xc00052d000?})
        /root/project/op-node/rollup/derive/deriver.go:133 +0x598
github.com/ethereum-optimism/optimism/op-node/rollup/event.(*DeriverMux).OnEvent(0x0?, {0x1d3b260, 0xc00052d000})
        /root/project/op-node/rollup/event/events.go:47 +0x3e
github.com/ethereum-optimism/optimism/op-program/client/driver.(*Driver).RunComplete(0xc0005342d0)
        /root/project/op-program/client/driver/driver.go:90 +0xd8
github.com/ethereum-optimism/optimism/op-program/client/tasks.RunDerivation({0x1d4d058, 0xc000192658}, _, _, {0x93, 0x54, 0x28, 0x72, 0x8b, 0xcf, ...}, ...)
        /root/project/op-program/client/tasks/derive.go:46 +0x41e
github.com/ethereum-optimism/optimism/op-program/client.RunProgram({0x1d4d058, 0xc000192658}, {0x1d3e098, 0xc000243b20}, {0x1d3e098, 0xc000243b30})
        /root/project/op-program/client/program.go:44 +0x337
github.com/ethereum-optimism/optimism/op-program/client.Main({0x1d4d058, 0xc000192658})
        /root/project/op-program/client/program.go:23 +0x66
main.main()
        /root/project/op-program/client/cmd/main.go:21 +0x6c

[tynes]

/ci authorize 5c48c9d