The wasm::manager is just cql3::wasm_context renamed. It now sits in
lang/wasm* and is started as a sharded service in main (and cql test
env). This move also needs some headers shuffling, but it's not severe
This change is required to make it possible for the wasm::manager to be
shared (by reference) between q.p. and replica::database further
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>