Migrate proxygen/lib/http/webtransport TARGETS to BUCK

Summary:
Merges `fbcode/proxygen/lib/http/webtransport/TARGETS` (10 targets) into a dirsynced `BUCK`.
This is the most entangled leaf: it has both name divergence (fbcode `webtransport` /
`httpwebtransport` / `webtransportimpl` / `quicwebtransport` / `wt_hq_session` vs monolith
`proxygen_webtransport` / `proxygen_httpwebtransport` / `proxygen_webtransportimpl` /
`proxygen_quicwebtransport` / lumped-in-`hq_session`) and granularity divergence (fbcode
`wt_util` + `flow_controller` are lumped into the monolith's `wt_stream_manager`;
`HqWtSession` is lumped into the monolith's `hq_session`). It is also consumed by the
already-migrated `lib/http/coro` and ~14 other targets, including flavored `...Android` /
`...Apple` refs in so-merge sequences.

- Adds the 10 fbcode cpp_library rules and 9 `non_fbcode_target` counterparts mirroring the
  monolith names and granularity.
- Because there are flavored external consumers (a plain `alias` does not regenerate
  `...Android` / `...Apple` sub-targets), the 8 monolith webtransport defs are replaced with
  thin `fb_xplat_cxx_library` forwards (name + platform flavors preserved, `exported_deps`
  point at the child), so `coro` and every other consumer are untouched.
- De-lumps `HqWtSession` out of the monolith `hq_session` (it now `exported_dep`s the child
  `wt_hq_session`).
- Prunes webtransport files (including the dead `QuicWtDeliveryCallbackWrapper.h` entry) from
  the `PROXYGEN_QUIC_SESSION_CONNECTION_*` / `PROXYGEN_HTTP_SERVER_FULL_*` lists and points
  `proxygen-quic_session_connection` / `proxygen-httpserver-full` at the child targets.

Reviewed By: mzlee

Differential Revision: D114611507

fbshipit-source-id: 87adc55d8a3c2061734030bbef0e8eb800c41483

Author: bigfootjon

proxygen/lib/http/webtransport/CMakeLists.txt

@@ -98,6 +98,7 @@ proxygen_add_library(proxygen_http_webtransport_wt_util
     proxygen_http_codec_webtransport_webtransport_capsule_codec
     proxygen_http_webtransport_wt_stream_manager
     Folly::folly_executor
+    Folly::folly_io_async_async_base
 )
 
 proxygen_add_library(proxygen_http_webtransport_webtransport_session