RFR: 8359437: Make users and test suite not able to set LockingMode flag

[David Holmes]

On Tue, 17 Jun 2025 08:39:49 GMT, Anton Artemov <duke at openjdk.org> wrote:

> This PR contains changes for the 1st phase of the `LockingMode` flag obsoletion. 
> 
> The work is done by @fbredber, I have taken it over and am finishing it while he's on vacation. 
> 
> In the 1st phase one keeps the `LockingMode` variable in all places, but makes it non-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 (phase 2).
> 
> Lightweight locking is the default locking from now on.
> 
> Tested in tiers 1 - 7.

Bug management issue should be fixed.

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PR Comment: https://git.openjdk.org/jdk/pull/25847#issuecomment-2999459491