Updated the documentation for -XX:+MergeCompilerOptions

[luke-li-2003]

Included descriptions and examples when used with -Xint, -Xnoaot, and -Xnojit.

[luke-li-2003]

@mpirvu

[pshipton]

@Sreekala-Gopakumar fyi

There are What's New and release notes to update as well. These either need to be included in PRs or an issue created for Sreekala to do it.

[pshipton]

If this is for 0.48, it can't be merged now or it will affect the docs for 0.47 (Java 23).

[mpirvu]

If this is for 0.48, it can't be merged now or it will affect the docs for 0.47 (Java 23).

This PR intends to add more clarity to the documentation for -XX:+MergeCompilerOptions.
Typically, -Xjit options that appear on the command line before -Xint or -Xnojit are ignored. However, this is not the case if -XX:+MergeCompilerOptions is also present on the command line. -XX:+MergeCompilerOptions will concatenate all -Xjit options, even those appearing before a -Xint (or -Xnojit). I wanted this behavior to be clearly spelled-out in the documentation.

This PR is not critical and can wait until 0.47 is released.

[pshipton]

If it's just for clarity and not related to any code change, then no What's New or release notes are required. It can be merged any time, and we could even update the 0.46 documentation to include it.