Delete abandoned segment parsing code (#82458)
Originally, as part of the clientParamParsing feature, I expected that I
would omit param values from the FlightRouterState when sending data
from the server, and add it on the client.
However, I've since realized this is unnecessary because
FlightRouterState is only used during runtime server responses. Not in
static responses, like per-segment prefetches.
Since the goal of clientParamParsing is to omit param values from static
responses, we don't need to change anything about FlightRouterState.
We may still want to update how params are processed on the server to
more closely match the implementation on the client, but that still
doesn't require any changes to FlightRouterState.
So, this deletes all the code related to adding client-parsed params to
FlightRouterState on the client. None of this was being used anywhere;
it was added by previous PRs in anticipation that it would eventually be
used. But now we don't need it.
