Support multiple identities for TLS 1.3 PSK

Description of the feature:

Support multiple identities for PSK in TLS 1.3 as per RFC 8446 4.2.11.

Applications that this feature may be relevant to:

NVMe-over-Fabrics TLS encryption has defined several possible identities per client. To correctly support TLS 1.3 the client would need to include all of those identities in the Pre-Shared-Key ClientHello extension. With gnutls this is currently not possible, and so we have to restart negotiation when the wrong PSK had been presented.

Is this feature implemented in other libraries (and which)

Not that I am aware.