RFR: 8269537: memset() is called after operator new

[Leo Korinth]

The basic problem is that we are relying on undefined behaviour, as documented in the code:

// This whole business of passing information from ResourceObj::operator new
// to the ResourceObj constructor via fields in the "object" is technically UB.
// But it seems to work within the limitations of HotSpot usage (such as no
// multiple inheritance) with the compilers and compiler options we're using.
// And it gives some possibly useful checking for misuse of ResourceObj.


I am removing the undefined behaviour by passing the type of allocation through a thread local variable.

This solution has some advantages:
1) it is not UB
2) it is simpler and easier to understand
3) it uses less memory (I could make it use even less if I made the enum `allocation_type` a u8)
4) in the *very* unlikely situation that stack memory (or embedded) already equals the data calculated from the address of the object, the code will also work. 

When doing the change, I also updated  `allocated_on_stack()` to the new name `allocated_on_stack_or_embedded()` which is much harder to misinterpret.

I also disallow to "fake" the memory type by explicitly calling `ResourceObj::set_allocation_type`.

This forced me to change two places that is faking the allocation type of an embedded `GrowableArray` from  `STACK_OR_EMBEDDED` to `C_HEAP`. The faking of the type is hard to understand as a `STACK_OR_EMBEDDED` `GrowableArray` can allocate any type of object. My guess is that `GrowableArray` has changed behaviour, or maybe that it was hard to understand because the old naming of `allocated_on_stack()`. 

I have also tried to update the comments. In doing that I not only changed the comments for this change, but also for the *incorrect* advice to always delete object you allocate with new.

Testing on debug build tier1-3
Testing on release build tier1

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Commit messages:
 - 8269537: memset() is called after operator new

Changes: https://git.openjdk.java.net/jdk/pull/5387/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5387&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269537
  Stats: 109 lines in 8 files changed: 1 ins; 66 del; 42 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5387.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5387/head:pull/5387

PR: https://git.openjdk.java.net/jdk/pull/5387