Expose an initializer function for non-abstract contracts in their upgradeable versions (#5008)

Co-authored-by: Hadrien Croubois <[email protected]>

Author: ernestognw

Diff for: .changeset/thin-walls-drop.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`AccessManager`, `VestingWallet`, `TimelockController` and `ERC2771Forwarder`: Added a public `initializer` function in their corresponding upgradeable variants.

Diff for: scripts/upgradeable/transpile.sh

@@ -38,7 +38,10 @@ npx @openzeppelin/upgrade-safe-transpiler -D \
   -x '!contracts/proxy/ERC1967/ERC1967Utils.sol' \
   -x '!contracts/proxy/utils/UUPSUpgradeable.sol' \
   -x '!contracts/proxy/beacon/IBeacon.sol' \
-  -p 'contracts/**/presets/**/*' \
+  -p 'contracts/access/manager/AccessManager.sol' \
+  -p 'contracts/finance/VestingWallet.sol' \
+  -p 'contracts/governance/TimelockController.sol' \
+  -p 'contracts/metatx/ERC2771Forwarder.sol' \
   -n \
   -N 'contracts/mocks/**/*' \
   -q '@openzeppelin/'