Verify Thread against upstream OpenJDK 8u121-b13.

Did some minor reformatting to improve consistency with upstream.

started field
- Moved to be adjacent to the threadStatus field which it replaces, in
  part. Documented how the started field corresponds to Thread.State
  and threadStatus.

threadStatus field
- Replaced remaining usage with started and commented out completely.
  The threadStatus field is initialized to 0 by default and is never
  modified, even by native code. That means that the test:
    (threadStatus != 0 || started)
  is equivalent to:
    (false || started)
  which is:
    (started)

blockedOn()
- Kept patch to make this @hide public as it is used by
  java.nio.channels.spi.AbstractInterruptibleChannel

sleep()
- Kept improved parameter validation patch as it provides more
  meaningful error messages, will add them to list of patchs that we
  could potentially upstream. Kept remaining Android specific patch to
  implement sleep() in Java using a native helper method as it attempts
  nanosecond (as opposed to millisecond) accuracy and moving the
  implementation to make it purely native as it is upstream would be
  costly in terms of development time and risky for no real benefit.

init(...)
- The call to setName() was replaced with upstream code to explicitly
  check the name parameter and set the name field. It behaves exactly as
  the call to setName() would, even though setName() does more than just
  set the field. i.e. setName()
  * calls checkAccess() but that is a noop final method.
  * sets the name of the native thread if it is active, nativePeer != 0.
    However, nativePeer == 0 at the point setName() was called from the
    init() method.

- Reorganized the initialization to make it as close to upstream as
  possible.

<init>()/init2() methods
- Kept Android specific constructor as it is used by the runtime when
  creating the adb connection thread. Similarly, the init2() method
  encapsulates functionality that is needed by both the standard and
  Android specific constructors.

start()
- Remove usage of threadStatus as it always evaluated to false.
  The threadStatus field is initialized to 0 by default and is never
  modified, even by native code. That means that the test:
    (threadStatus != 0 || started)
  is equivalent to:
    (false || started)
  or simply:
    (started)

- Kept patches to change started from local variable to a field and to
  use the Android specific native method to create/start the thread.

stop()
- Changed it to simply throw an UnsupportedOperationException directly
  as that is what it previously did and it is no longer the same as
  upstream so we have to keep a patch anyway. Updated JavaDoc too.

stop(Throwable)
- Added synchronized keyword to match upstream as it makes no difference
  as the method should not be being called.

interrupt()
- Kept patch to rename upstream interrupt0() as nativeInterrupt(). Will
  investigate as part of the follow up bug whether this can be reverted.

interrupted()/isInterrupted()
- Kept patch but provided detailed explanation as to the difference
  from upstream. Will investigate as part of the follow up bug whether
  this can be reverted.

destroy()
- Kept patch to throw UOE instead of NoSuchMethodError.

isAlive()
- Kept patch to implement using pure Java.

suspend()/resume()
- Kept patches to throw UOE as upstream has been deprecated and method
  is deadlock-prone.

setPriority()
- Kept patches to throw more meaningful exception, to synchronize
  around setting the priority and to avoid calling the native method if
  the thread has not yet started.

setName(String)
- Added synchronized keyword and removed synchronized(this) block to
  match upstream. The moving of the checkAccess() and null check out of
  the synchronized block is not worth maintaining a patch.

getThreadGroup()
- Kept patch to correct behavior when the thread has been terminated
  but improved documentation.

countStackFrames()
- Kept patch to provide Java implementation, is less efficient than a
  native method but it is deprecated and it is unlikely anyone uses it.

join()
- Kept patch to sychronize on separate lock object rather than the
  current Thread. Could not find any clear explanation why this change
  was made.

checkAccess()/getContextClassLoader()/setContextClassLoader()/
setDefaultUncaughtExceptionHandler()
- Kept patches to comment out security code.

getStackTrace()
- Kept patch to implement in terms of VMStack.

getAllStackTraces()
- Restructured a little to more closely match upstream.

getState()
- Kept patch to use started instead of threadStatus.

uncaughtExceptionPreHandler and methods
- Kept patch as is used by platform.

Kept the patch to support park/unpark.

During this work some issues were found that require further work and
investigation. These are recorded in b/80180276.

Tested using:
  make checkbuild, flash and CtsLibcoreTestCases
  art/test/testrunner/run_build_test_target.py -j80 art-test

The latter was needed because some art tests depend on implementation
details of the Thread class, e.g. its allocated size, call stack for
native methods currentThread() and getState().

Bug: 74379469
Test: As above

Change-Id: Id9c9c37b764f13a1eb719521b05b8467a454d716

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