Prototype integration of mlkem-native into AWS-LC

[hanno-becker]

This issue tracks the work towards integration-readiness of mlkem-native into AWS-LC. It is not about an actual integration. The expectation is that demonstrating integration-readiness will flush out a lot of usability issues, esp. given the special FIPS build requirements of AWS-LC.

• mlkem-native with C backend (only) successfully integrates AWS-LC with minimal changes. Demonstrated against a fork of AWS-LC and exercised in CI. Only basic tests to be run (e.g. cmake --target run_tests)
• mlkem-native with native backends successfully integrates AWS-LC with minimal changes. Demonstrated against a fork of AWS-LC and exercised in CI. Only basic tests to be run (e.g. cmake --target run_tests)

[hanno-becker]

#654 (in progress) works towards the first checkpoint.