Allow skipping the AWS CLI profile creation in `configure`

**Is your feature request related to a problem? Please describe.**

I'm having many AWS accounts to manage, and therefore already many profiles. For security reasons I have my AWS configuration (`~/.aws` directory) mounted read-only, and I prefer to not have arbitrary tools modify these. Instead _I_ manage the settings, and would just select the correct profile explicitly whenever using any AWS-related tool.

I'm right now following the AWS Amplify tutorial, and the `amplify configure` just did a couple of things I have issues with:
1. It expects to be fed the credentials. Given that this is a new tool (at least for me), and installed from npm without any specific version or anything, I rather not do that.
2. It also expects that it can modify the ~/.aws/credentials (and probably other files), and will crash in half-finished state (probably) when it can't:
~~~~
Enter the access key of the newly created user:
? accessKeyId: ********************
? secretAccessKey: ****************************************
This would update/create the AWS Profile in your local machine
? Profile Name: amplify-tutorial
EROFS: read-only file system, chmod '.../.aws/credentials'
Error: EROFS: read-only file system, chmod '.../.aws/credentials'
at Object.chmodSync (fs.js:1205:3)
at Object.chmodSync (.../modules/nvs/node/12.19.0/x64/lib/node_modules/@aws-amplify/cli/node_modules/graceful-fs/polyfills.js:252:21)
at makeFileOwnerReadWrite (.../modules/nvs/node/12.19.0/x64/lib/node_modules/@aws-amplify/cli/node_modules/amplify-provider-awscloudformation/src/system-config-manager.js:98:6)
at Object.setProfile (.../modules/nvs/node/12.19.0/x64/lib/node_modules/@aws-amplify/cli/node_modules/amplify-provider-awscloudformation/src/system-config-manager.js:19:5)
at Object.run (.../modules/nvs/node/12.19.0/x64/lib/node_modules/@aws-amplify/cli/node_modules/amplify-provider-awscloudformation/src/setup-new-user.js:113:25)
at processTicksAndRejections (internal/process/task_queues.js:97:5)
~~~~

**Describe the solution you'd like**

1. Minimally: Handle the EROFS, by providing a "skip", or "try again" option.
2. Ideally: Allow me to enter the name of the profile to use instead of walking through creating a user.

Given that the tutorial only says "run this", I would expect the tool to be very clear and safe to use (i.e. be very defensive on error cases, and allow me to handle whatever local world I have).

**Describe alternatives you've considered**

I actually hoped that it would handle the error and provide a "skip" option, or maybe tell me how to restart the process.

Another option could be to provide indication how to run the tool with an existing user account (think `AWS_PROFILE=my-profile amplify configure`; the tool could check with `sts:GetCallerIdentity` if things are fine) -- but I really don't know where else this information wants to be stored now to know whether this is feasible.