Fix ByteBody stream writing for HTTP/2

[yawkat]

The writer wrote ByteBufs directly instead of HttpContent, which works for HTTP/1 but not HTTP/2. Also improved error handling.

Fixes #11260

Draft until @asw12 signs the CLA for the test case

[CLAassistant]

All committers have signed the CLA.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[asw12]

All committers have signed the CLA.

@yawkat Done! Thank you for the fast turnaround.