Non-zero `exitCode` is not accessible from `exec`/`getExecOutput` with `ignoreReturnCode: false`

Describe the enhancement
When ignoreReturnCode: false is set and a process exits with a non-zero exit code, an Error is thrown. This error contains the message The process '${this.toolPath}' failed with exit code ${this.processExitCode} but has no direct access to the exit code and would need to be parsed from the message as a workaround.

Compare this to ignoreReturnCode: true, which has the exitCode readily accessible.

let { exitCode, stdout, stderr } = await exec.getExecOutput(
  'ls', ['package.json'], 
  {ignoreReturnCode: true}
)

Code Snippet

try {
  // Non-zero exits will proceed to `catch`
  let { exitCode, stdout, stderr } = await exec.getExecOutput(
    'ls', ['package.json'], 
    {ignoreReturnCode: false}
  )
} catch (error) {
   // Exit code is not accessible in `error.exitCode`
}

Additional information
Related code: https://github.com/actions/toolkit/blob/main/packages/exec/src/toolrunner.ts#L530-L534

Start at packages/exec/src/toolrunner.ts around lines 530-534 and compare the error path with the ignoreReturnCode: true result. Make the non-zero exit code available directly on the caught error, then verify that callers no longer need to parse it from the message.