RFR: 8342941: IGV: Add new graph dumps for post loop, empty loop removal, and one iteration removal [v2]

[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))

Saranya Natarajan has updated the pull request incrementally with one additional commit since the last revision:

  Addressing review comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25756/files
  - new: https://git.openjdk.org/jdk/pull/25756/files/767326bf..e4dab565

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25756&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25756&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 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