[Suggestion] Function to get v8 heap information

[andreespirela]

The suggestion is to get the heap information from v8, this would behave slightly similar to NodeJS api. https://nodejs.org/api/v8.html#v8_v8_getheapsnapshot .

It would be good to have

• Deno.getHeapSpaceStatistics()
• Deno.getHeapSnapshot()
• Deno.getHeapStatistics()
• Deno.getHeapCodeStatistics()

Ideally, for now, it would be very useful to have: Deno.getHeapSnapshot

Optionally, you could put the 4 mentioned API's together in a v8 object such as Deno.v8 : Deno.v8.getHeapSpaceStatistics

[kitsonk]

Related #1569