[x] Add NewAttestationReportFetcher5 and NewAttestationReportFetcher6
[x] Change behavior of NewAttestationReportFetcher so that it returns either resut of NewAttestationReportFetcher5 or NewAttestationReportFetcher6 when possible. Otherwise return error.
[x] Use the new feature in the sidecars
Test
[x] Test attestation-container and related package in Confidential ACI with kernel 5.x
[x] Test attest package with 6.x
[ ] Test attestation-container with 6.x
[ ] My 6.x environment can't access the Internet (So can't use azure cache servers now)
Change
Test