feat: add support for NEW_RELIC_APP_NAME environment variable

[Sashwatdas123]

Details:

Adds a new --app-name CLI flag that sets the NEW_RELIC_APP_NAME environment variable on instrumented Lambda functions.

Usage

newrelic-lambda layers install --function <name> --nr-account-id <id> --app-name 'my-app'

Behavior

• If --app-name is provided, NEW_RELIC_APP_NAME is set in Environment variables of lambda
• If --upgrade is passed with a different value, the existing NEW_RELIC_APP_NAME is updated
• If --app-name is omitted, any existing NEW_RELIC_APP_NAME is left untouched
• On layers uninstall, NEW_RELIC_APP_NAME is removed along with other New Relic env vars

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.10%. Comparing base (59b796b) to head (622c7a3).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #371      +/-   ##
==========================================
+ Coverage   70.04%   70.10%   +0.06%     
==========================================
  Files          20       20              
  Lines        1876     1880       +4     
==========================================
+ Hits         1314     1318       +4     
  Misses        562      562              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.