[threads][test][js-api] Add tests for growing shared memory

[backes]

Add a few first (!) js-api test to this repo. In particular:

• Growing a non-shared memory always detaches the old buffer and allocates a fresh one (as before).
• Growing a shared memory only refreshes the buffer if the delta in pages is > 0.
• Growing a shared memory has no effect on unrelated shared memories.

Note that V8 didn't implement this correctly until https://crrev.com/c/7660970, see https://crbug.com/492128992.