feat(api-rest): support timeout configuration for rest api.

[Simone319]

Description of changes

Support timeout configuration for rest api, on 2 different levels:

• Per API request level
• Library options level via amplify.configure()

Issue #, if available

#13426
#6526

Description of how you validated changes

Run e2e tests: https://github.com/aws-amplify/amplify-js/actions/runs/18162727003 (failing tests are not rest api related)
Verified with local Amplify app.

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced) -> Will follow up after release

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

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