[keyvault-certificates] Upgrade to @azure/eslint-plugin-azure-sdk@^3.0.0

[willmtemple]

Keyvault is still using version 2 of the eslint plugin. This issue is to track upgrading it to version 3. Instructions below,

See also #7147 #7148

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The gist of how this works is to basically do the following steps in the package directory:

1. Add a dependency on the new version (3.0.0) of the plugin to your devDepdendencies:

"@azure/eslint-plugin-azure-sdk": "^3.0.0"

you also need to make sure the following are also devDependencies (due to how eslint resolves plugins, you need all plugins that are used by the configuration as direct devDependencies):

"@typescript-eslint/eslint-plugin": "^2.0.0"
"@typescript-eslint/parser": "^2.0.0"
"eslint": "^6.1.0"
"eslint-plugin-no-null": "^1.0.2"
"eslint-plugin-no-only-tests": "^2.3.0"
"eslint-plugin-promise": "^4.1.1"

2. Create .eslintrc.json with these contents:

{
  "plugins": ["@azure/azure-sdk"],
  "extends": ["plugin:@azure/azure-sdk/azure-sdk-base"]
}

3. Change the lint and lint:fix commands in the package.json file to the following:

    "lint:fix": "eslint package.json api-extractor.json src test --ext .ts --fix --fix-type [problem,suggestion]",
    "lint": "eslint package.json api-extractor.json src test --ext .ts -f html -o search-lintReport.html || exit 0",

4. Make sure the eslint plugin is built. A safe way is to build the tree of your package's dependencies again:

rush update
rush build -t @azure/<package-name>

Make sure it says it built @azure/eslint-plugin-azure-sdk in the process.

5. Run the linter and check the output:

rushx lint

then open the lint report HTML file in the package directory.

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You might find that you need to disable some of the rules temporarily while we can work out fixes for them. Just log an issue with the eslint-plugin tag for any that you find.