Switch coverage from nyc to c8 (#3398)

.c8rc.json

@@ -0,0 +1,22 @@
+{
+  "all": true,
+  "include": ["src/"],
+  "exclude": [
+    "src/**/index.ts",
+    "src/**/*-fuzz.ts",
+    "src/jsutils/Maybe.ts",
+    "src/jsutils/ObjMap.ts",
+    "src/jsutils/PromiseOrValue.ts",
+    "src/utilities/typedQueryDocumentNode.ts"
+  ],
+  "clean": true,
+  "temp-directory": "coverage",
+  "report-dir": "coverage",
+  "skip-full": true,
+  "reporter": ["json", "html", "text"],
+  "check-coverage": true,
+  "branches": 100,
+  "lines": 100,
+  "functions": 100,
+  "statements": 100
+}

.eslintrc.yml

@@ -22,7 +22,6 @@ rules:
   internal-rules/only-ascii: error
   internal-rules/no-dir-import: error
   internal-rules/require-to-string-tag: off
-  internal-rules/require-coverage-ignore-reason: error
 
   ##############################################################################
   # `eslint-plugin-node` rule list based on `v11.1.x`