Use Head to validate sidecars when possible (#15977)

* Use Head to validate sidecars when possible

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>

* LazyHeadStateProvider that avoids service registry

* Remove extra file

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: james-prysm <90280386+james-prysm@users.noreply.github.com>
Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>

beacon-chain/execution/BUILD.bazel

@@ -100,6 +100,7 @@ go_test(
     deps = [
         "//async/event:go_default_library",
         "//beacon-chain/blockchain/kzg:go_default_library",
+        "//beacon-chain/blockchain/testing:go_default_library",
         "//beacon-chain/cache/depositsnapshot:go_default_library",
         "//beacon-chain/core/feed:go_default_library",
         "//beacon-chain/core/feed/state:go_default_library",

beacon-chain/execution/service_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/OffchainLabs/prysm/v7/async/event"
+	chainMock "github.com/OffchainLabs/prysm/v7/beacon-chain/blockchain/testing"
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/cache/depositsnapshot"
 	dbutil "github.com/OffchainLabs/prysm/v7/beacon-chain/db/testing"
 	mockExecution "github.com/OffchainLabs/prysm/v7/beacon-chain/execution/testing"
@@ -99,7 +100,7 @@ func TestStart_OK(t *testing.T) {
 	c := startup.NewClockSynchronizer()
 	require.NoError(t, c.SetClock(startup.NewClock(time.Unix(0, 0), [32]byte{})))
 	waiter := verification.NewInitializerWaiter(
-		c, forkchoice.NewROForkChoice(nil), nil)
+		c, forkchoice.NewROForkChoice(nil), nil, &chainMock.ChainService{})
 
 	web3Service, err := NewService(t.Context(),
 		WithHttpEndpoint(endpoint),