sharkd: Remove json order restriction

The "method" root member previously needed to be in front of level 2 parameters inside of the json string.

This commit removes the order restriction by first obtaining the "method" before continuing the normal process of checking/obtaining values. A valid json string would now also be: {"jsonrpc":"2.0", "params":{"file":"info.pcapng"}, "id":1, "method":"load"}

Closes #17824 (closed)