MINOR: task: set execution context on task/tasklet calls

MINOR: task: set execution context on task/tasklet calls

It now appears almost everywhere due to callbacks (e.g. ssl_sock_io_cb).
Muxes also become visible now on memory profiling. A small test on h1+ssl
yields 838 lines of statistics. The number of buckets should definitely
be increased, and more grouping criteria should be added.

A performance test was conducted to observe the possible effect of
setting the execution context on each task switch, and it didn't change
at all, remaining at about 1.01 billion ctxsw/s on a 128-thread EPYC.