three-args contructor to SkMemoryStream not exposed.

[HinTak]

Is your feature request related to a problem? Please describe.

You actually use the under-lying 3-argument ptr-len-bool constructor for MemorySream to process 2-arg buffer-bool inputs:

skia-python/src/skia/Stream.cpp

Line 652 in cd03964

new SkMemoryStream(info.ptr, size, copyData));

I actually needs the raw 3-argument to process input with (non-null-terminated string, len, boolean)

Describe the solution you'd like

Expose the raw 3-arg method to take 3 arguments.

Describe alternatives you've considered

Currently I am using Data(ptr, len) to build a buffer in python first. But I found the raw 3-arg method when I was programming using c++ instead, then go back to check how the python method is bound.

Additional context
The input is just in two pieces, non-null-terminated pointer and length. It is more natural just to pass these along like in c++, instead of wrapping a Data(ptr, len) around it.