RFR: 8342941: IGV: Add new graph dumps for post loop, empty loop removal, and one iteration removal

[Saranya Natarajan]

This changeset adds BEFORE/AFTER graph dumps for creating a post loop (`insert_post_loop()`), removing an empty loop (`do_remove_empty_loop()`), and removing a one iteration loop (`do_one_iteration_loop()`).

Changes:
- Added `BEFORE_POST_LOOP` and `AFTER_POST_LOOP` for dumping graphs before and after `insert_post_loop()`.
- Added `BEFORE_REMOVE_EMPTY_LOOP` and `AFTER_REMOVE_EMPTY_LOOP` for dumping graphs before and after `do_remove_empty_loop()`.
- Added `BEFORE_ONE_ITERATION_LOOP` and `AFTER_ONE_ITERATION_LOOP` for dumping graphs before and after `do_one_iteration_loop()`.

Below are sample screenshots (IGV print level 4 ) mainly showing the new phase .
1. `BEFORE_POST_LOOP` and `AFTER_POST_LOOP` 
![image](https://github.com/user-attachments/assets/1661cede-5d70-4e0d-abec-3d091c7675c8)
2. `BEFORE_POST_LOOP` and `AFTER_POST_LOOP` with SuperWordLoopUnrollAnalysis enabled
![image](https://github.com/user-attachments/assets/6a22e6f0-4e6c-4e9d-8b6b-2bf75fac783d)
3.` BEFORE_REMOVE_EMPTY_LOOP `and `AFTER_REMOVE_EMPTY_LOOP`
![image](https://github.com/user-attachments/assets/3281f00b-575e-4604-83dd-831037d8dd47)
4. `BEFORE_ONE_ITERATION_LOOP` and `AFTER_ONE_ITERATION_LOOP`
![image](https://github.com/user-attachments/assets/efddbc9a-64f7-403d-acfe-330d75a00911)

Question to reviewers:
Are the new compiler phases OK, or should we change anything?

Testing:
GitHub Actions
tier1 to tier5 on windows-x64, linux-x64, linux-aarch64, macosx-x64, and macosx-aarch64.
Tested that thousands of graphs are correctly opened and visualized with IGV using the same test used in ([JDK-8317349](https://bugs.openjdk.org/browse/JDK-8317349))

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Commit messages:
 - Initial Fix

Changes: https://git.openjdk.org/jdk/pull/25756/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25756&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342941
  Stats: 19 lines in 3 files changed: 19 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25756.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25756/head:pull/25756

PR: https://git.openjdk.org/jdk/pull/25756