style(ctb): move legacy contracts to legacy folder (#3043)

Moves various legacy contracts into the legacy folder. Purpose of the
legacy folder is to explicitly mark the contracts that we're trying to
push users away from. By moving these contracts into the legacy folder,
we're creating a clearer message that users should be using alternatives
and should not be using these contracts after Bedrock.
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.changeset/hot-panthers-think.md

+---
+'@eth-optimism/contracts-bedrock': patch
+---
+
+Moves various legacy contracts into the legacy folder

packages/contracts-bedrock/.storage-layout

@@ -108,13 +108,13 @@
 ➡ DeployerWhitelist
 =======================
 
-+-----------+--------------------------+------+--------+-------+------------------------------------------------------+
++-----------+--------------------------+------+--------+-------+----------------------------------------------------------+
 | Name      | Type                     | Slot | Offset | Bytes | Contract                                                 |
-+=====================================================================================================================+
-| owner     | address                  | 0    | 0      | 20    | contracts/L2/DeployerWhitelist.sol:DeployerWhitelist |
-|-----------+--------------------------+------+--------+-------+------------------------------------------------------|
-| whitelist | mapping(address => bool) | 1    | 0      | 32    | contracts/L2/DeployerWhitelist.sol:DeployerWhitelist |
-+-----------+--------------------------+------+--------+-------+------------------------------------------------------+
++=========================================================================================================================+
+| owner     | address                  | 0    | 0      | 20    | contracts/legacy/DeployerWhitelist.sol:DeployerWhitelist |
+|-----------+--------------------------+------+--------+-------+----------------------------------------------------------|
+| whitelist | mapping(address => bool) | 1    | 0      | 32    | contracts/legacy/DeployerWhitelist.sol:DeployerWhitelist |
++-----------+--------------------------+------+--------+-------+----------------------------------------------------------+
 
 =======================
 ➡ GasPriceOracle

packages/contracts-bedrock/contracts/L2/L1BlockNumber.sol → packages/contracts-bedrock/contracts/legacy/L1BlockNumber.sol

 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.10;
 
-import { L1Block } from "./L1Block.sol";
+import { L1Block } from "../L2/L1Block.sol";
 import { Predeploys } from "../libraries/Predeploys.sol";
 import { Semver } from "../universal/Semver.sol";
 

packages/contracts-bedrock/contracts/test/DeployerWhitelist.t.sol

@@ -2,7 +2,7 @@
 pragma solidity 0.8.10;
 
 import { CommonTest } from "./CommonTest.t.sol";
-import { DeployerWhitelist } from "../L2/DeployerWhitelist.sol";
+import { DeployerWhitelist } from "../legacy/DeployerWhitelist.sol";
 
 contract DeployerWhitelist_Test is CommonTest {
     DeployerWhitelist list;

packages/contracts-bedrock/contracts/test/L1BlockNumber.t.sol

@@ -3,7 +3,7 @@ pragma solidity 0.8.10;
 
 import { Test } from "forge-std/Test.sol";
 import { L1Block } from "../L2/L1Block.sol";
-import { L1BlockNumber } from "../L2/L1BlockNumber.sol";
+import { L1BlockNumber } from "../legacy/L1BlockNumber.sol";
 import { Predeploys } from "../libraries/Predeploys.sol";
 
 contract L1BlockNumberTest is Test {