[Core][AWS] Allow specification of IAM roles for resources.

[JGSweets]

This PR updates the schema config to allow specification of IAM roles for resources based on the skypilot naming conventions.

Address: https://github.com/skypilot-org/skypilot/issues/3487

In ~/.sky/config.yaml:

• When setting for the controller and all other resources (default)

aws:
  remote_identity:
    sky-serve-controller-*: skypilot-v1-fake
    "*": skypilot-default-fake

• When setting for everything by specifying a default

aws:
  remote_identity:
    "*": skypilot-default-fake

• When setting for everything by specifying just the remote_identity via string

aws:
  remote_identity: skypilot-default-fake

• When first profile doesn't match it chooses the next in line if viable

aws:
  remote_identity:
    does-not-match: skypilot-default-fake
    "*": skypilot-default-fake

Tested (run the relevant ones):

• [x] Code formatting: bash format.sh
• [x] Any manual or new tests for this PR (please specify below)
  • tested running in all 4 configs in AWS
    • Nothing set
    • setting different controller and default values
    • setting default only
    • setting two profile names where the first one doesn't match to ensure it selects the viable candidate in order
• [ ] All smoke tests: pytest tests/test_smoke.py
• [ ] Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• [ ] Backward compatibility tests: bash tests/backward_comaptibility_tests.sh

[JGSweets]

Due note the quotes required around * to meet yaml file specifications: "*".

e.g.

aws:
  remote_identity:
    "*": skypilot-default-fake

[JGSweets]

@Michaelvll Fixed as suggested. Thanks for the improvements!