Release 4.4.0

[benoitc]

Cut 4.4.0 (minor). Since 4.3.0:

• HTTP/2 streaming request bodies and streaming response reads, reaching parity with HTTP/1.1 and HTTP/3 (Bump h2 to ~>0.10.0 and add HTTP/2 streaming bodies #875).
• Full-duplex HTTP/2 bidirectional streaming via the new h2_* API, mirroring ws_* / wt_* (Add HTTP/2 full-duplex bidirectional stream API (h2_*) #876).
• h2 0.9.0 -> ~> 0.10.0.

Updates NEWS.md, the README feature list, and bumps vsn to 4.4.0.