Prevent plasma ionization past the atomic number

[AlexanderSinn]

@lucafedeli88 found an out-of-bounds memory access in #1340 which could have caused ions to ionize to higher levels than they would have had electrons. In my quick test, the probability of ionizing too high ended up being zero, however this was not guaranteed. This changes the RNG results for ionization.

• Small enough (< few 100s of lines), otherwise it should probably be split into smaller PRs
• Tested (describe the tests in the PR description)
• Runs on GPU (basic: the code compiles and run well with the new module)
• Contains an automated test (checksum and/or comparison with theory)
• Documented: all elements (classes and their members, functions, namespaces, etc.) are documented
• Constified (All that can be const is const)
• Code is clean (no unwanted comments, )
• Style and code conventions are respected at the bottom of https://github.com/Hi-PACE/hipace
• Proper label and GitHub project, if applicable

[lucafedeli88]

Thanks for the quick fix, @AlexanderSinn . I am testing your solution here: #1344

[lucafedeli88]

After your fix the sanitizer does not find any other error.

[MaxThevenet]

Thanks for this fix!

[lucafedeli88]

Thanks for this quick fix, @AlexanderSinn