RFR: 8354675: Create separate image builder for hermetic

[Severin Gehwolf]

This is a start of a simple refactoring for moving hermetic handling into dedicated implementation classes. In this case I cover `ImageBuilder` and `ExecutableImage`. A similar change should be done for `ImageFileCreator` but that's for another PR.

@jianglizhou Please take a look. Thanks!

While at it I've observed the following:

1. `<hermetic-image-file> --list-modules` doesn't seem to work. Shows [1] for me.
2. `strip -g <hermetic-image-file>` will destroy the image. Looks like [2]. Probably a drawback for tucking on the offset after the modules file? We might want to consider building in debuginfo handling into `jlink` itself. Like the `--strip-native-debug-symbols` plugin does (but doesn't work for hermetic, yet).

Thoughts?

[1]

$ ./demo-image -m mod.example/com.example.demo.Main
[0.017s][warning][cds] Failed to open shared archive file (Not a directory)
Hi
$
./demo-image --list-modules
[0.020s][warning][cds] Failed to open shared archive file (Not a directory)
Exception in thread "main" java.lang.InternalError: Unable to detect the run-time image
	at java.base/jdk.internal.module.SystemModuleFinders.ofSystem(Unknown Source)
	at java.base/java.lang.module.ModuleFinder.ofSystem(Unknown Source)
	at java.base/jdk.internal.module.ModuleBootstrap.unlimitedFinder(Unknown Source)
	at java.base/jdk.internal.module.ModuleBootstrap.limitedFinder(Unknown Source)
	at java.base/sun.launcher.LauncherHelper.listModules(Unknown Source)


[2] This is a build with `--with-native-debug-symbols=internal` (fastdebug)

$ ll -lh ./demo-image 
-rwxr-xr-x. 1 sgehwolf sgehwolf 909M Apr 10 17:36 ./demo-image
$ strip -g ./demo-image 
$ ll -lh ./demo-image 
-rwxr-xr-x. 1 sgehwolf sgehwolf 50M Apr 10 18:07 ./demo-image
$ ./demo-image -m mod.example/com.example.demo.Main
Error occurred during initialization of VM
Failed setting boot class path.

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

Commit messages:
 - Create a separate image builder for hermetic

Changes: https://git.openjdk.org/leyden/pull/55/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=55&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354675
  Stats: 165 lines in 3 files changed: 138 ins; 21 del; 6 mod
  Patch: https://git.openjdk.org/leyden/pull/55.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/55/head:pull/55

PR: https://git.openjdk.org/leyden/pull/55