OpenPMDWriter.cpp & HpMultiGrid.H : enforce clang-tidy rule bugprone-branch-clone

[lucafedeli88]

This PR is a follow-up of #1302 .
By using the tool proposed in #1303 I ran clang-tidy on the code. This PR fixes the issues found with the rule:

• bugprone-branch-clone

Is this something that you would like to enforce in HiPACE++ ? In my opinion, most of the checks of the bugprone-* family are quite useful (in WarpX we decided to enable most of them)...

These are the only issues found with the following rules:

    bugprone-argument-comment,
    bugprone-assert-side-effect,
    bugprone-assignment-in-if-condition,
    bugprone-bad-signal-to-kill-thread,
    bugprone-bitwise-pointer-cast,
    bugprone-bool-pointer-implicit-conversion,
    bugprone-branch-clone,
    bugprone-casting-through-void,
    bugprone-chained-comparison,
    bugprone-compare-pointer-to-member-virtual-function,
    bugprone-copy-constructor-init,
    bugprone-crtp-constructor-accessibility,
    bugprone-dangling-handle,
    bugprone-dynamic-static-initializers,
    cppcoreguidelines-avoid-goto

• 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

[AlexanderSinn]

Hmm, I feel like the old way is more readable as it looks closer to get_num_comps_acf below it.

[lucafedeli88]

If you want uniformity of style, one option would be to change also get_num_comps_acf by writing:

switch (system_type) {
    case 1:
        return 1;
    case 2:
        return 2;
    case 3:
        return 0;
}

There's also the option of disregarding the rule if you don't like it.

[AlexanderSinn]

I discussed this with Emanuele on what is more readable, and it is ok to do it the clang-tidy way if also the formatting in get_num_comps_acf is updated.

[lucafedeli88]

Done!

[AlexanderSinn]

Thanks for this PR!