RE: [Proposal] Add foreign-server health checks infrastructure

Dear Ted,

Thanks for reviewing! PSA new version.

> For v25-0001-Add-PQConnCheck-and-PQCanConnCheck-to-libpq.patch , `pqConnCheck_internal` only has one caller which is
quiteshort.
 
> Can pqConnCheck_internal and PQConnCheck be merged into one func ?

I divided the function for feature expandability. Currently it works on linux platform,
but the limitation should be removed in future and internal function will be longer.
Therefore I want to keep this style.

> +int
> +PQCanConnCheck(void)
>
> It seems the return value should be of bool type.

I slightly changed the returned value like true/false. But IIUC libpq functions
cannot define as "bool" datatype. E.g. PQconnectionNeedsPassword() returns true/false,
but the function is defined as int.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED