RFR: 8341293: Split field loads through Nested Phis

[Dhamoder Nalla]

As an extension of the work done as part of https://github.com/openjdk/jdk/pull/12897, split the field loads (AddP -> Load*) with nested phi parent nodes to enable more scalar replacements, thereby reducing memory allocation.


Here are the sequence of Ideal graph transformations for Nested phi:

 
![image](https://github.com/user-attachments/assets/c18e5ca0-c554-475c-814a-7cb288d96569)

![image](https://github.com/user-attachments/assets/b279b5f2-9ec6-4d9b-a627-506451f1cf81)

![image](https://github.com/user-attachments/assets/f506b918-2dd0-4dbe-a440-ff253afa3961)

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Commit messages:
 - Fix trailing whitespaces
 - Split load fields through nestead phi nodes

Changes: https://git.openjdk.org/jdk/pull/21270/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21270&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341293
  Stats: 1687 lines in 7 files changed: 1598 ins; 38 del; 51 mod
  Patch: https://git.openjdk.org/jdk/pull/21270.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21270/head:pull/21270

PR: https://git.openjdk.org/jdk/pull/21270