Introduce Thread Safe Map Data Structure

[rauljordan]

This PR introduces a basic, thread-safe map data structure that is type-safe due to generics. It has a dead-simple API, and performance is very close to a concrete data structure. We should aim to use this anywhere where we create locks for the sole purpose of securing a lonely map in Prysm

Bench:

goos: linux
goarch: amd64
pkg: github.com/prysmaticlabs/prysm/v3/container/thread-safe
cpu: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
BenchmarkMap_Concrete-8            19357             62184 ns/op
BenchmarkMap_Generic-8             19231             64920 ns/op
PASS

func BenchmarkMap_Concrete(b *testing.B) {
	mm := &safeMap{
		items: make(map[int]string),
	}
	for i := 0; i < b.N; i++ {
		for j := 0; j < 1000; j++ {
			mm.Put(j, "foo")
			mm.Get(j)
			mm.Delete(j)
		}
	}
}

func BenchmarkMap_Generic(b *testing.B) {
	items := make(map[int]string)
	mm := NewThreadSafeMap(items)
	for i := 0; i < b.N; i++ {
		for j := 0; j < 1000; j++ {
			mm.Put(j, "foo")
			mm.Get(j)
			mm.Delete(j)
		}
	}
}

[nisdas]

Depending on what type K is you might run into the for loop reference bug, where the reference changes with each iteration and in the slice. Since this is generic and to safeguard against all types, you should copy k before appending it to r

[rauljordan]

let's just get rid of this method because there is no way of copying k generically unless it implements some Copy method

[nisdas]

sorry not a deep copy, but just copy the value . Ex:

copiedK := k
r = append(r, copiedK)

[rauljordan]

Pushed