linux: add Expanding_cpu_session_client

This is needed for upgrading the Cpu_session's quota to pay
for the tracebuffer.
fixup base-linux
fixup Trace_buffer mem -> Events
fixup Trace_fs
fixup base-foc thread_start
fixup core Trace_registry
fixup _main start-up
fixup trace_session test
fixup cpu_session_component
fixup noux trace_fs run
XXX increase memory in noux_tool_chain_nova.run