Fix tracing.NewRandomRatioBased panic

[alanprot]

What this PR does:
Fix the NewRandomRatioBased panic.

This sampler were using a random - which is not thread safe:

// NewSource returns a new pseudo-random Source seeded with the given value.
// Unlike the default Source used by top-level functions, this source is not
// safe for concurrent use by multiple goroutines.
func NewSource(seed int64) Source {
	var rng rngSource
	rng.Seed(seed)
	return &rng
}

goroutine 514103346 [running]:
math/rand.(*rngSource).Uint64(...)
	/opt/brazil-pkg-cache/packages/GoLang/GoLang-1.x.108333.0/AL2_x86_64/DEV.STD.PTHREAD/build/lib/src/math/rand/rng.go:249
math/rand.(*rngSource).Int63(0x0?)
	/opt/brazil-pkg-cache/packages/GoLang/GoLang-1.x.108333.0/AL2_x86_64/DEV.STD.PTHREAD/build/lib/src/math/rand/rng.go:234 +0x92
math/rand.(*Rand).Int63(...)
	/opt/brazil-pkg-cache/packages/GoLang/GoLang-1.x.108333.0/AL2_x86_64/DEV.STD.PTHREAD/build/lib/src/math/rand/rand.go:84
math/rand.(*Rand).Float64(0xc000893b30)
	/opt/brazil-pkg-cache/packages/GoLang/GoLang-1.x.108333.0/AL2_x86_64/DEV.STD.PTHREAD/build/lib/src/math/rand/rand.go:195 +0x30
golang.a2z.com/AWSPrometheusCortex/vendor/github.com/cortexproject/cortex/pkg/tracing/sampler.(*RandomRatioBased).ShouldSample(0xc000893b60, {{0x28a1ef0, 0xc34f531710}, {0x63, 0x9b, 0x55, 0x68, 0x6d, 0xcb, 0x45, ...}, ...})

This PR change the sample decision to be based on the random part of the trace Id.

Checklist

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

[yeya24]

LGTM

[alanprot]

I created a PR on the otel contrib: open-telemetry/opentelemetry-go-contrib#3090

Lets see if get merged.