Use 63 bits for Beam ID

[AlexanderSinn]

In this PR, 63 bits of the idcpu component are used to store the id, instead of the 40 bits dedicated for the id. What previously was in the cpu component, the MR level, is now stored in a new component mr_level that does not need to be communicated with MPI.

This will prevent the ID from looping around if there are more than 2^31 particles.

Test with 3*10^9 Gaussian particles (180GB beam output per time step); openPMD iteration 7:

id.shape=(2999630696,)
id[:100]=array([  1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,
        14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,
        27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  37,  38,  39,
        40,  41,  42,  43,  44,  45,  46,  47,  48,  49,  50,  51,  52,
        53,  54,  55,  56,  57,  58,  59,  60,  61,  62,  63,  64,  65,
        66,  67,  68,  69,  70,  71,  72,  73,  74,  75,  76,  77,  78,
        79,  80,  81,  82,  83,  84,  85,  86,  87,  88,  89,  90,  91,
        92,  93,  94,  95,  96,  97,  98,  99, 100], dtype=uint64)
id[-100:]=array([2999630597, 2999630598, 2999630599, 2999630600, 2999630601,
       2999630602, 2999630603, 2999630604, 2999630605, 2999630606,
       2999630607, 2999630608, 2999630609, 2999630610, 2999630611,
       2999630612, 2999630613, 2999630614, 2999630615, 2999630616,
       2999630617, 2999630618, 2999630619, 2999630620, 2999630621,
       2999630622, 2999630623, 2999630624, 2999630625, 2999630626,
       2999630627, 2999630628, 2999630629, 2999630630, 2999630631,
       2999630632, 2999630633, 2999630634, 2999630635, 2999630636,
       2999630637, 2999630638, 2999630639, 2999630640, 2999630641,
       2999630642, 2999630643, 2999630644, 2999630645, 2999630646,
       2999630647, 2999630648, 2999630649, 2999630650, 2999630651,
       2999630652, 2999630653, 2999630654, 2999630655, 2999630656,
       2999630657, 2999630658, 2999630659, 2999630660, 2999630661,
       2999630662, 2999630663, 2999630664, 2999630665, 2999630666,
       2999630667, 2999630668, 2999630669, 2999630670, 2999630671,
       2999630672, 2999630673, 2999630674, 2999630675, 2999630676,
       2999630677, 2999630678, 2999630679, 2999630680, 2999630681,
       2999630682, 2999630683, 2999630684, 2999630685, 2999630686,
       2999630687, 2999630688, 2999630689, 2999630690, 2999630691,
       2999630692, 2999630693, 2999630694, 2999630695, 2999630696],
      dtype=uint64)

• 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