options: Support arbitrarily long pattern buffers

options: Support arbitrarily long pattern buffers

Dynamically allocate the pattern buffer to remove the 512B length
restriction. To accomplish this, store a pointer instead of a fixed
block of memory for the buffers in the thread_options structure.
Then introduce and use the function parse_and_fill_pattern_alloc()
which will calculate the approprite size of the buffer and allocate
it before filling it.

The buffers will be freed, along with a number of string buffers
in free_thread_options_to_cpu(). They will also be reallocated (if
necessary) when receiving them over the wire with
convert_thread_options_to_cpu().

This allows for specifying real world compressible data (eg. The
Calgary Corpus) for the buffer_pattern option.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>