RFR: 8350287: Cleanup SA's support for CodeBlob subclasses [v2]

[Chris Plummer]

> There is a lot of subclassing of CodeBlob types done in SA to mimic hotspot, but most of it is unnecessary. The generic CodeBlob class can handle all support needed by most of the subclasses. The only subclasses we need to keep around around NMethod, RuntimeStub, and UpcallStub, since they all have special support in SA. I also kept around RuntimeBlob so RuntimeStub can continue to inherit from it and be consistent with hotspot, but it's not actually necessary, and I'm more than happy to remove it also.
> 
> I also cleaned up the PStack support for CodeBlobs. It can just use CodeBlob.getName() rather than trying to figure out the type of the CodeBlob instance to print out type name. This allows us to get rid of most isXXX() APIs. It also provides more useful output in some cases. 
> 
> There is some minor loss of functionality in some of the CodeBlob subtypes I removed. For example this is what AdapterBlob.getName() looked like (it is now gone):
> 
> 
>   public String getName() {
>     return "AdapterBlob: " + super.getName();
>   }
> 
> 
> So now we just use the default CodeBlob.getName(), which is what super.getName() would up execute. I think for AdapterBlob this always returns "I2C/C2I adapters", so now you only get this rather than "AdapterBlob: I2C/C2I adapters". We have a similar loss of getName() detail with MethodHandlesAdapterBlob (now returns "MethodHandles adapters") and VtableBlob (now returns "vtable chunks"). Basically for these 3 CodeBlob types getName() will no longer include the CodeBlob type.  I could special case them in CodeBlob.getName() by fetching the kind to determine what the proper name should be. Let me know if you think it is worth it.

Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:

  Minor improvements.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23684/files
  - new: https://git.openjdk.org/jdk/pull/23684/files/138fed50..e965c310

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23684&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23684&range=00-01

  Stats: 110 lines in 4 files changed: 4 ins; 104 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23684.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23684/head:pull/23684

PR: https://git.openjdk.org/jdk/pull/23684