Enhance management of certificates rejected by the PKI

PKI API, file src/Common/crypto/lib_dep/mbedtls/pki_mbedtls.c:

• We should delete the rejected certificate once it is added as trusted / accepted.
• The bAppendRejectCert field in SOPC_PKI_Profile should be removed as it is not used.
• SOPC_PKIProvider_AddCertToRejectedList should be updated to add a rejected certificate only if it is not already included in the list. This would simplify the SOPC_PKIProvider_CopyRejectedList function (its processing would only make a copy)
• The function SOPC_PKIProvider_WriteRejectedCertToStore should be reworked to replace the old rejected files in the store with the current certificates. Indeed, the internal buffer storing the current rejected certificates is circular (a kind of ring buffer) and its contents is always up to date.