cleanup generated env file on deploy

[ykethan]

Environment information

System:
  OS: macOS 14.7.1
  CPU: (8) arm64 Apple M1
  Memory: 142.02 MB / 16.00 GB
  Shell: /bin/zsh
Binaries:
  Node: 22.10.0 - /opt/homebrew/bin/node
  Yarn: 1.22.21 - ~/.nvm/versions/node/v20.2.0/bin/yarn
  npm: 10.9.0 - /opt/homebrew/bin/npm
  pnpm: 9.8.0 - /opt/homebrew/bin/pnpm
NPM Packages:
  @aws-amplify/auth-construct: 1.3.1
  @aws-amplify/backend: 1.5.1
  @aws-amplify/backend-auth: 1.2.0
  @aws-amplify/backend-cli: 1.2.9
  @aws-amplify/backend-data: 1.1.5
  @aws-amplify/backend-deployer: 1.1.5
  @aws-amplify/backend-function: 1.7.1
  @aws-amplify/backend-output-schemas: 1.4.0
  @aws-amplify/backend-output-storage: 1.1.2
  @aws-amplify/backend-secret: 1.1.4
  @aws-amplify/backend-storage: 1.2.1
  @aws-amplify/cli-core: 1.1.3
  @aws-amplify/client-config: 1.5.0
  @aws-amplify/deployed-backend-client: 1.4.1
  @aws-amplify/form-generator: 1.0.3
  @aws-amplify/model-generator: 1.0.8
  @aws-amplify/platform-core: 1.1.0
  @aws-amplify/plugin-types: 1.3.0
  @aws-amplify/sandbox: 1.2.3
  @aws-amplify/schema-generator: 1.2.4
  aws-amplify: 6.6.5
  aws-cdk: 2.162.1
  aws-cdk-lib: 2.162.1
  typescript: 5.6.3
AWS environment variables:
  AWS_STS_REGIONAL_ENDPOINTS = regional
  AWS_NODEJS_CONNECTION_REUSE_ENABLED = 1
  AWS_SDK_LOAD_CONFIG = 1
No CDK environment variables

Describe the bug

the env files generated for a lambda function in .amplify/generated/env are not cleaned up.
For example if the function was renamed or function was deleted. The env import or sandbox deploy will not throw any error as the file is not cleaned up. The deploy will fail on amplify hosting as the file will not generate.

Reproduction steps

1. Add a Lambda function
2. import env object in handler
3. rename Lambda function

[ykethan]

PR addressing this: #2054