[kernel] Add endpoint object and related syscalls

The endpoint object adds synchronous IPC. Also added the wait-type of
'object' to threads.

modules.yaml

@@ -38,6 +38,7 @@ modules:
             - src/kernel/memory_bootstrap.cpp
             - src/kernel/msr.cpp
             - src/kernel/objects/channel.cpp
+            - src/kernel/objects/endpoint.cpp
             - src/kernel/objects/kobject.cpp
             - src/kernel/objects/thread.cpp
             - src/kernel/objects/process.cpp
@@ -51,6 +52,7 @@ modules:
             - src/kernel/syscall.cpp
             - src/kernel/syscall.s
             - src/kernel/syscalls/channel.cpp
+            - src/kernel/syscalls/endpoint.cpp
             - src/kernel/syscalls/object.cpp
             - src/kernel/syscalls/process.cpp
             - src/kernel/syscalls/system.cpp