metamorphic: consider running with configurations that alter the compression library

[nicktrav]

We currently test with the default codec (snappy at the time of writing). To give us better coverage, we should consider testing against configurations with a) a different codec to standard-000, and b) an LSM with a mixture of codecs for various levels (as opposed to the same library for all levels).

We'd update the code here, to set the codec, and possibly have a mixture of level configs:

pebble/internal/metamorphic/options.go

Lines 264 to 270 in 3355a02

	var lopts pebble.LevelOptions
	lopts.BlockRestartInterval = 1 + rng.Intn(64) // 1 - 64
	lopts.BlockSize = 1 << uint(rng.Intn(24)) // 1 - 16MB
	lopts.BlockSizeThreshold = 50 + rng.Intn(50) // 50 - 100
	lopts.IndexBlockSize = 1 << uint(rng.Intn(24)) // 1 - 16MB
	lopts.TargetFileSize = 1 << uint(rng.Intn(28)) // 1 - 256MB
	opts.Levels = []pebble.LevelOptions{lopts}