util/fastuuid: delete unused package

Its sole user was deleted in 02cafbe1ca.

And it has no public users: https://pkg.go.dev/tailscale.com/util/fastuuid?tab=importedby

And nothing in other Tailsale repos that I can find.

Updates tailscale/corp#24721

Change-Id: I8755770a255a91c6c99f596e6d10c303b3ddf213
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

util/fastuuid/fastuuid.go

@@ -1,56 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-// Package fastuuid implements a UUID construction using an in process CSPRNG.
-package fastuuid
-
-import (
-	crand "crypto/rand"
-	"encoding/binary"
-	"io"
-	"math/rand/v2"
-	"sync"
-
-	"github.com/google/uuid"
-)
-
-// NewUUID returns a new UUID using a pool of generators, good for highly
-// concurrent use.
-func NewUUID() uuid.UUID {
-	g := pool.Get().(*generator)
-	defer pool.Put(g)
-	return g.newUUID()
-}
-
-var pool = sync.Pool{
-	New: func() any {
-		return newGenerator()
-	},
-}
-
-type generator struct {
-	rng rand.ChaCha8
-}
-
-func seed() [32]byte {
-	var r [32]byte
-	if _, err := io.ReadFull(crand.Reader, r[:]); err != nil {
-		panic(err)
-	}
-	return r
-}
-
-func newGenerator() *generator {
-	return &generator{
-		rng: *rand.NewChaCha8(seed()),
-	}
-}
-
-func (g *generator) newUUID() uuid.UUID {
-	var u uuid.UUID
-	binary.NativeEndian.PutUint64(u[:8], g.rng.Uint64())
-	binary.NativeEndian.PutUint64(u[8:], g.rng.Uint64())
-	u[6] = (u[6] & 0x0f) | 0x40 // Version 4
-	u[8] = (u[8] & 0x3f) | 0x80 // Variant 10
-	return u
-}

util/fastuuid/fastuuid_test.go

@@ -1,72 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package fastuuid
-
-import (
-	"testing"
-
-	"github.com/google/uuid"
-)
-
-func TestNewUUID(t *testing.T) {
-	g := pool.Get().(*generator)
-	defer pool.Put(g)
-	u := g.newUUID()
-	if u[6] != (u[6]&0x0f)|0x40 {
-		t.Errorf("version bits are incorrect")
-	}
-	if u[8] != (u[8]&0x3f)|0x80 {
-		t.Errorf("variant bits are incorrect")
-	}
-}
-
-func BenchmarkBasic(b *testing.B) {
-	b.Run("NewUUID", func(b *testing.B) {
-		for range b.N {
-			NewUUID()
-		}
-	})
-
-	b.Run("uuid.New-unpooled", func(b *testing.B) {
-		uuid.DisableRandPool()
-		for range b.N {
-			uuid.New()
-		}
-	})
-
-	b.Run("uuid.New-pooled", func(b *testing.B) {
-		uuid.EnableRandPool()
-		for range b.N {
-			uuid.New()
-		}
-	})
-}
-
-func BenchmarkParallel(b *testing.B) {
-	b.Run("NewUUID", func(b *testing.B) {
-		b.RunParallel(func(pb *testing.PB) {
-			for pb.Next() {
-				NewUUID()
-			}
-		})
-	})
-
-	b.Run("uuid.New-unpooled", func(b *testing.B) {
-		uuid.DisableRandPool()
-		b.RunParallel(func(pb *testing.PB) {
-			for pb.Next() {
-				uuid.New()
-			}
-		})
-	})
-
-	b.Run("uuid.New-pooled", func(b *testing.B) {
-		uuid.EnableRandPool()
-		b.RunParallel(func(pb *testing.PB) {
-			for pb.Next() {
-				uuid.New()
-			}
-		})
-	})
-}