chore(op-reth): move op-dependent examples into crates/optimism/examples/ (#21495)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

Cargo.toml

@@ -77,6 +77,10 @@ members = [
     "crates/optimism/cli",
     "crates/optimism/consensus",
     "crates/optimism/evm/",
+    "crates/optimism/examples/custom-node",
+    "crates/optimism/examples/engine-api-access",
+    "crates/optimism/examples/exex-hello-world",
+    "crates/optimism/examples/op-db-access",
     "crates/optimism/flashblocks/",
     "crates/optimism/hardforks/",
     "crates/optimism/node/",
@@ -145,7 +149,6 @@ members = [
     "examples/beacon-api-sse/",
     "examples/bsc-p2p",
     "examples/custom-dev-node/",
-    "examples/custom-node/",
     "examples/custom-engine-types/",
     "examples/custom-evm/",
     "examples/custom-hardforks/",
@@ -154,10 +157,7 @@ members = [
     "examples/custom-payload-builder/",
     "examples/custom-rlpx-subprotocol",
     "examples/custom-rpc-middleware",
-    "examples/custom-node",
     "examples/db-access",
-    "examples/engine-api-access",
-    "examples/exex-hello-world",
     "examples/exex-subscription",
     "examples/exex-test",
     "examples/full-contract-state",
@@ -168,7 +168,6 @@ members = [
     "examples/node-builder-api/",
     "examples/node-custom-rpc/",
     "examples/node-event-hooks/",
-    "examples/op-db-access/",
     "examples/polygon-p2p/",
     "examples/rpc-db/",
     "examples/precompile-cache/",