First try of removing LockingMode

[fbredber]

This is a draft PR that contains my first try of removing the LockingMode option, and fix the tests that would otherwise break when removing that option.

This means that in this first try I'll keep the LockingMode variable, but it will not be settable from the command line, all the C1 and C2 code related to legacy locking will still be in place (but as dead code) and removed later. I'm doing it this way just to get my head around what needs to be done up front to remove the LockingMode option from a user perspective.
Lightweight locking is the default locking, but the -XX:LockingMode=0, which is monitor locking, can now be set by using -XX:+UseHeavyMonitors. This system made it much easier to go through and fix all the test.

This draft PR covers parts of these JBS enhansments:

• JDK-8344261 Obsolete the LockingMode flag and related code
• JDK-8336325 Add back UseHeavyMonitors as a develop option

It's probably a good idea to break up this PR into several sub tasks that fall into the above enhancements.

This draft PR is mostly here as a basis for having a discussion on how to move forward.

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Progress

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Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25660/head:pull/25660
$ git checkout pull/25660

Update a local copy of the PR:
$ git checkout pull/25660
$ git pull https://git.openjdk.org/jdk.git pull/25660/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25660

View PR using the GUI difftool:
$ git pr show -t 25660

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25660.diff

[bridgekeeper]

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[openjdk]

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[openjdk]

@fbredber this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout _remove_locking_mode_fix_tests
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push