* Moved samples around to meet new recommendations; added a couple of additional tests.
* Reworked attestation to include RetrieveAttestationValidationCollateral
* Attestation sample readme updates
* TPM doesn't need to retrieve response validation collateral
* Added cautionary warning about the dangers of overriding the TearDown method from inside a test case
* Added attestation team members to codeowners for attestation SDK
* Remove CODEOWNERS from cspell checks
* Don't hold a lock across retrieving the signers over the network
* Updated snippets in readme; clang-format
