VMFB buffer access test

[renxida]

This test mimics the kvcache indexing, reading, and writing in open-llama-3b-v2-f16.gguf.

It's a simple test to verify that shortfin can:

• Create device arrays
• Map and fill them
• Invoke a VMFB and pass arguments to it
• Properly retain changes made by the VMFB to device arrays provided as arguments

[renxida]

used to be #325, which was reverted because it broke CI

[renxida]

Compared to #325 this has 2 code changes:

• no more np dependency
• skipped for windows
  and some name / docstring /comment changes.

[kumardeepakamd]

We should try to get it fixed for windows before merging.

[kumardeepakamd]

Thanks for enabling it for Windows too.