Address a long-standing semantic confusion in EGSnrc. The term "restart"
has been used ambiguously to describe resuming a simulation after an
interruption (e.g., a power failure). Use "resume" instead to accurately
reflect continuing from where the simulation left off. Restarting
conveys the idea that the simulation is starting over from the
beginning.

Address another long-standing semantic confusion in EGSnrc. The term
"restart" was used ambiguously to describe rewinding a phase space file
after reaching the end, when more particles are requested. Use "rewind"
to accurately reflect starting from the beginning of the file again,
aligning with the programming concept of rewinding a file.

Eliminate the last occurrences of "restart" in the EGSnrc repository.
Previously, "restart" was used ambiguously to mean relaunching a
process, resuming a simulation, or rewinding a phase space file. These
actions are now distinctly referred to as "relaunch", "resume", and
"rewind". To avoid confusion with past terminology, the generic term
"restart" is no longer used in EGSnrc, as of this commit.