RFR(sh/jdk8): [backport] 8240315: Shenandoah: Rename ShLBN::get_barrier_strength()

[Roman Kennke]

> On 12/1/20 1:52 PM, Roman Kennke wrote:
>> This is a backport of:
>> https://bugs.openjdk.java.net/browse/JDK-8240315
>>
>> It is very straightforward.
>>
>> Testing: hotspot_gc_shenandoah
>>
>> Ok?
> 
> No webrev again :)

http://cr.openjdk.java.net/~rkennke/JDK-8240315-jdk8/webrev.00/