CesiumCurl dependency on libcurl doesn't enable key features like HTTP2

[kring]

The vcpkg curl port has non-default features for lots of pretty important stuff, like support for HTTP2. That means our default build of CesiumCurl doesn't support HTTP2, which is pretty important for our use-cases. We should go through the list of features and decide which ones we want to enable.

[azrogers]

Seems to me like the list is brotli, http2, http3, idn2, non-http, openssl, and maybe zstd. non-http should be necessary for FTP support (along with a bunch of other protocols I don't think anyone will care for, like Gopher). I don't think we have to worry about people obtaining tilesets over LDAP or websockets or anything like that, and many of the other options are just configuring which library (primarily which SSL library) curl uses.