wip: trying to debug why we have an extra data frame in the client streaming st case

[mgodave]

Problem

The blocking servicetalk server sends an extra empty data frame on failure even when there aren't any trailers. This causes some issues for the grpc-java client.

Changes

I added a filter and a context key to signal when we have a case where we can avoid sending the extra empty data frame. In the "BROKEN AFTER CHANGE" case below I expect not to see the extra data frame as I am in the previous case but I assume I'm missing a detail about how ST works to be able to be effective in debugging this rn.

Results

Before Change:

OUTBOUND HEADERS: streamId=3 headers=GrpcHttp2OutboundHeaders[:authority: 127.0.0.1:62451, :path: /grpc.netty.Compat/clientStreamingCall, :method: POST, :scheme: http, content-type: application/grpc, te: trailers, user-agent: grpc-java-netty/1.64.1, grpc-accept-encoding: gzip] streamDependency=0 weight=16 exclusive=false padding=0 endStream=false
OUTBOUND DATA: streamId=3 padding=0 endStream=false length=7 bytes=00000000020801
OUTBOUND DATA: streamId=3 padding=0 endStream=true length=0 bytes=
INBOUND HEADERS: streamId=3 headers=GrpcHttp2ResponseHeaders[:status: 200, server: servicetalk-grpc/, content-type: application/grpc+proto, grpc-status: 12, grpc-message: Method grpc.netty.Compat/clientStreamingCall is unimplemented] padding=0 endStream=false
INBOUND DATA: streamId=3 padding=0 endStream=true length=0 bytes=

After Change:

### WORKING AFTER CHANGE (grpc -> ST blocking)
OUTBOUND HEADERS: streamId=3 headers=GrpcHttp2OutboundHeaders[:authority: 127.0.0.1:62421, :path: /grpc.netty.Compat/clientStreamingCall, :method: POST, :scheme: http, content-type: application/grpc, te: trailers, user-agent: grpc-java-netty/1.64.1, grpc-accept-encoding: gzip] streamDependency=0 weight=16 exclusive=false padding=0 endStream=false
OUTBOUND DATA: streamId=3 padding=0 endStream=false length=7 bytes=00000000020801
OUTBOUND DATA: streamId=3 padding=0 endStream=true length=0 bytes=
INBOUND HEADERS: streamId=3 headers=GrpcHttp2ResponseHeaders[:status: 200, server: servicetalk-grpc/, content-type: application/grpc+proto, grpc-status: 12, grpc-message: Method grpc.netty.Compat/clientStreamingCall is unimplemented, content-length: 0] padding=0 endStream=true

[mgodave]

Closed in favor or #3152