wireproto: drop the _decompress method in favor a new call type
We already have multiple call function for multiple return type. The
`_decompress` function is only used for http and seems like a layer violation.
We drop it in favor of a new call type dedicated to "stream that may be useful to
compress".
Testing that hghave does not crash when checking features
$ "$TESTDIR/hghave" --test-features 2>/dev/null