ci: Fixes to codecov configuration

codecov.yml

@@ -1,20 +1,30 @@
-comment: true
+comment:
+  layout: "reach, diff, flags, files"
+  behavior: default
+  require_changes: true    # only post the comment if coverage changes
 ignore:
   - "l2geth"
   - "**/*.t.sol"
   - "op-bindings/bindings/*.go"
-  - "packages/contracts-bedrock/contracts/(vendor|libraries)/(trie|rlp)"
+  - "packages/contracts-bedrock/contracts/vendor/WETH9.sol"
+coverage:
+  status:
+    patch:
+      default:
+        target: auto  # target coverage is equal to the PR base
+        threshold: 0% # coverage is not allowed to reduce vs. the PR base
+        base: auto
 flag_management:
   # Note: flags should have the same name as the circleci job in which they
   # are uploaded.
   individual_flags:
-    - name: bedrock-go-tests
     - name: contracts-bedrock-tests
       paths:
         - packages/contracts-bedrock/contracts
       statuses:
         - type: patch
           target: 100%
+    - name: bedrock-go-tests
     - name: common-ts-tests
     - name: contracts-tests
     - name: core-utils-tests
@@ -27,20 +37,3 @@ flag_management:
     - name: message-relayer-tests
     - name: replica-healthcheck-tests
     - name: sdk-tests
-coverage:
-  status:
-    patch:
-      default:
-        # basic
-        target: auto
-        threshold: 0%
-        base: auto
-        # advanced
-        branches:
-          - master
-        if_ci_failed: error #success, error
-        only_pulls: false
-        flags:
-          - "unit"
-        paths:
-          - "src"