feat: add --all flag to remove all secrets in sandbox

[fossamagna]

Problem

Support the --all flag on sandbox secret remove to remove all secrets in a single command

Issue number, if available:

#2257

Changes

I change to use yargs.command instead of yargs.positional to handling the secret-name argument.
We can not set secret-name as optional argument when use yargs.positional without default value.
Instead of we can set secret-name as optional argument that using [secret-name] syntax in yargs.command

Corresponding docs PR, if applicable:

Validation

• Unit Tests
• Manual Tests

Checklist

• If this PR includes a functional change to the runtime behavior of the code, I have added or updated automated test coverage for this change.
• If this PR requires a change to the Project Architecture README, I have included that update in this PR.
• If this PR requires a docs update, I have linked to that docs PR above.
• If this PR modifies E2E tests, makes changes to resource provisioning, or makes SDK calls, I have run the PR checks with the run-e2e label set.

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

[changeset-bot]

🦋 Changeset detected

Latest commit: 1be27e1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@aws-amplify/backend-cli	Minor

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