RFR: 8289710: Move Suspend/Resume classes out of os.hpp [v2]

[Ioi Lam]

> Please review this simple change that only renames a few classes and moved some code around. No functional changes.
> 
> The following classes are used only sparingly. They should be moved to a new header file share/runtime/suspend.hpp to minimize the size of os.hpp
> 
> - SuspendedThreadTaskContext
> - SuspendedThreadTask
> - SuspendResume
> 
> I didn't move the OS-specific implementation to a new file -- the POSIX implementation is currently inside [signals_posix.cpp](https://github.com/openjdk/jdk/blob/df063f7db18a40ea7325fe608b3206a6dff812c1/src/hotspot/os/posix/signals_posix.cpp#L1790) mixed with other signal handling code, so it doesn't seem a good idea to move out just the code for the above 3 classes.
> 
> The only other implementation is in os_windows.cpp. I could move the code to suspend_windows.cpp, but I don't feel very motivated unless someone insists.

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  moved SuspendResume class to os/posix directory

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/9371/files
  - new: https://git.openjdk.org/jdk/pull/9371/files/2df83ec8..8265ecb2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9371&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9371&range=00-01

  Stats: 320 lines in 8 files changed: 187 ins; 130 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/9371.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9371/head:pull/9371

PR: https://git.openjdk.org/jdk/pull/9371