update libpq

[sdy3000]

Dear community

We are building Python wheel package for adbc_driver_postgresql locally to get later version of libpq in order to pick up the
newer client features, e.g. sslnegotiation=direct. The ABI is unchanged, so it seems to work smoothly.

I can see libpq is pinned in .env VCPKG= that points to libpq 16.9.
Latest is 18.4. https://github.com/microsoft/vcpkg/blob/master/ports/libpq/vcpkg.json
Are there other dependencies holding back on upgrading or is it already in the pipeline or a recurring task to bump compatible versions in the release cycles?

I'm just curious on the process and if it is w.i.p. I will just watch here patiently. Otherwise consider this post as a flag and at least I am sharing successful experience of bumping the libpq version.

thanks
Søren

[lidavidm]

We share some build Docker containers with apache/arrow; it seems we could bump the vcpkg commit forward slightly: https://github.com/apache/arrow/blob/6166ef59804cbae988954776704301656eb68c1a/.env#L95

A PR would be appreciated.