fix(amplify-cli-core): gracefully handle execa race condition

[rtpascual]

Description of changes

When execa handles a hooks file that executes very fast, we have a race condition where execa will try to pipe inputs to the child process's stdin after the process finishes causing an EPIPE error (Refer to sindresorhus/execa#474).

The change is to not have execa reject initially so we can determine what to do:

• If the hooks file executed successfully (child process exit code is 0), then we continue execution.
• If not, then we go through our existing error handling.

Also updated how we pipe stdout for the child process, this caused the misconception that the hooks file was not running at all (no echo in the hooks file is presented).

Issue #, if available

Description of how you validated changes

Added unit tests and manually tested with the following pre-push and post-push hooks files:

// pre-push.sh
echo "prepush hook"

// post-push.sh
echo "postpush hook"

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)
• New AWS SDK calls or CloudFormation actions have been added to relevant test and service IAM policies
• Pull request labels are added

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[rtpascual]

l_function_3a_init_special_case_http_migration E2E test, go function tests › add go hello world function and invoke in the cloud, failed and is being addressed as part of #13671