RFR: 8311071: Avoid SoftReferences in LambdaFormEditor and MethodTypeForm when storing heap objects into AOT cache

[ioi.lam at oracle.com]

Hi, this is the 6th PR for JEP 483 - Ahead-of-Time Class Loading & 
Linking [1]

The PR is https://github.com/openjdk/jdk/pull/21049

- When writing heap objects to the AOT cache (currently this is done 
only when dumping "static" CDS archive), avoid using SoftReferences in 
LambdaFormEditor and MethodTypeForm.
- This is a requirement by JDK-8293336 [3] (AOT-linking of invokedynamic 
for lambda expression and string concat), which is the 7th and last PR 
for JEP 483


The plan [2] is to break down JEP 483 in a series of 7 PRs to make it 
easier to review. I will post the other PRs soon.

Thanks

- Ioi

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[1] https://openjdk.org/jeps/483
[2] https://bugs.openjdk.org/browse/JDK-8331497
[3] https://bugs.openjdk.org/browse/JDK-8293336