TCP Proxy protocol V2 : store data as base64 string

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Title: Store TLV data of proxy protocol V2 as base64

Description: Proxy protocol V2 uses binary data for TLV. When using the tcp proxy filter, we are able to store the tlv data in the metadata as a string. Since it's binary, it would be more appropriate to store it as base64. Currently, when we try to log it, we get an error saying it contains invalid characters.