RFR(S/M): 8246476: remove AsyncDeflateIdleMonitors option and the safepoint based deflation mechanism

[Daniel D. Daugherty]

Greetings,

It's time to remove the AsyncDeflateIdleMonitors option from JDK16. We can
also get rid of the safepoint based deflation mechanism since turning off
async deflation (-XX:-AsyncDeflateIdleMonitors) was the only way left to
use it.

This is marked as an "S/M" review because the number of touched/deleted
lines makes it a Medium review, but the number of touched/changed lines
(outside of the deletions) makes it a Small review. It's actually a pretty
fast read... :-)

Here's the bug ID:

     JDK-8246476 remove AsyncDeflateIdleMonitors option and the safepoint
                 based deflation mechanism
     https://bugs.openjdk.java.net/browse/JDK-8246476

Here's the webrev URL:

     http://cr.openjdk.java.net/~dcubed/8246476-webrev/0_for_jdk16/

The webrev is baselined on Thomas S's fix for 8248650 which is jdk-16+4
plus a dozen or so changesets.

This change has been tested with Mach5 Tier[1-3],4,5,6,7,8 and there are
no regressions (and very few known failures). My inflation stress testing
is still in process. I had to restart that testing after a thunderstorm
related power failure took down my servers in Florida. Sigh...

Thanks, in advance, for any comments, questions, or suggestions.

Dan