EAMxx: allow perturbation of restart files (not just ic)

[mahf708]

in https://github.com/E3SM-Project/E3SM/blob/01d73b88efe3ae640aa0dfd5c29e3baef24dece7/components/eamxx/src/control/atmosphere_driver.cpp#L1380

we are able to perturb select fields in the IC so to create multiple trajectories. Unfortunately, this only happens if we are starting the model from scratch

https://github.com/E3SM-Project/E3SM/blob/01d73b88efe3ae640aa0dfd5c29e3baef24dece7/components/eamxx/src/control/atmosphere_driver.cpp#L872-L877

proposal: allow users to request a perturbation even in restart files, potentially with an additional runtime guard to ensure the user actually means they actually want this (in a way, a compounded perturbation since it will happen at every restart).

rationale: really helpful to navigate tricky waters/winds/instabilities

impl: add these to components/eamxx/cime_config/namelist_defaults_eamxx.xml as well so that hey are exposed as runtimes and add corresponding docs under components/eamxx/docs/user

caveat: the current impl of this perturbation is under the "initial_conditions" heading of runtime configuration,

https://github.com/E3SM-Project/E3SM/blob/01d73b88efe3ae640aa0dfd5c29e3baef24dece7/components/eamxx/cime_config/namelist_defaults_eamxx.xml#L730-L736

and so one would need to think about hijacking this section so that it applies to restart capabilities or a whole new set of duplicated params are used elsewhere in the namelist_defaults_eamxx.xml file.