Avoid a copy of security keys in publisher context when unnecessary

Description

When sending a networkMessage with security mode Sign or SignAndEncrypt publisher remove keys and get keys from SKS performing an allocation and a copy even if the keys hasn't changed.

To avoid a superficial copy check whether the received key from SKS are different from the one already stored.

Code version and environment identification

commit sha: 95fed1731

Steps to reproduce

N.A

Relevant logs and/or screenshots

N.A

Analysis

See description

Security impact

N.A

Possible fixes

Update function SOPC_PubSubSKS_GetSecurityKeys to take actual SOPC_PubSubSKS_Keys context to check if received SecurityTokenId is different from the one in used. Perform a copy of the keys only if these one are new.