SGX removal from main

[achamayou]

As per 5.0 release notes, release/5.x is the last LTS with SGX support. 6.0 (main at the moment) will target confidential containers exclusively, and switch from Ubuntu to Azure Linux 3.0.

This issue tracks the various steps involved in the removal of SGX from main, the list is a work-in-progress:

• [x] Remove SGX attestation verifcation/oehostverify dependency from virtual and snp builds (#6423)
• [x] Remove SGX target (but keep build-* image creation for SGX to support 5.x/4.x) (#6426)
• [x] Remove CCF_DISABLE_VERBOSE_LOGGING (#6426)
• [x] Remove SGX from release playbooks, but keep it in ccf-dev for build-* images (#6447)
• [ ] Migrate code upgrade tests from SGX to Virtual
• [ ] Merge SNP and Virtual targets, SNP presence is detected at runtime
• [ ] Remove INSIDE_ENCLAVE