scylla-gdb.py: managed_bytes_printer: print blobs in hex format
scylla-gdb.py: managed_bytes_printer: print blobs in hex format

Currently blobs are converted to python bytes objects and printed by
simply converting them to string. This results in hard to read blobs as
the bytes' __str__() attempts to interpret the data as a printable
string. This patch changes this to use bytes.hex() which prints blobs in
hex format. This is much more readable and it is also the format that
scylla uses when printing blobs.

Also the conversion to bytes is made more efficient by using gdb's
gdb.inferior.read_memory() function to read the data.

Signed-off-by: Botond Dénes <a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>
Message-Id: <20200911085439.1461882-1-a584fa4d75a0a85d721f44fb6e06315a2853b0b6@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla