Versioned WAL

[joe-elliott]

What this PR does:
Reuses all of the existing versioned code to enabled versioned WALs. This includes the ability to compress the WAL which addresses #418.

Benchmarks:

goos: linux
goarch: amd64
pkg: github.com/grafana/tempo/tempodb/wal
cpu: Intel(R) Core(TM) i7-8565U CPU @ 1.80GHz
BenchmarkWALNone-8     	     132	   8162877 ns/op	 2543406 B/op	   38124 allocs/op
BenchmarkWALSnappy-8   	     135	   8712571 ns/op	 2657195 B/op	   36621 allocs/op
BenchmarkWALLZ4-8      	      84	  13025362 ns/op	 5149115 B/op	   49653 allocs/op
BenchmarkWALGZIP-8     	      36	  34852004 ns/op	 3893758 B/op	   40209 allocs/op
BenchmarkWALZSTD-8     	      21	  47785689 ns/op	49718721 B/op	  112807 allocs/op
PASS
ok  	github.com/grafana/tempo/tempodb/wal	7.972s

The benchmarks do not reveal a clear winner here so I'm leaving None as the default and documenting the ability to turn this on. We will experiment with snappy internally.

Which issue(s) this PR fixes:
Fixes #418

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[mdisibio]

Left a few thoughts