adds sslinline option to postgres conn string

[bhoriuchi]

• for database secrets type postgres, inspects the connection string for sslinline and generates a tlsconfig from the connection string.
• standard operation of the driver expects sslcert, sslkey, and sslrootcert to be file paths
• the workaround cleans the connection string of all ssl and uses the stdlib.RegisterConnConfig method to add a new connection with a custom tlsconfig. most of the code is forked/ported from the github.com/jackc/pgconn package because the functions are not exposed.

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[fairclothjm]

Hi @bhoriuchi, thanks for the contribution. We will need to review this more internally before we can decisively say we can accept it.