[RM-8183] [Parameters][Structure] From linemodelsolve.linemodel remove .linemodel + homogenize names

Created on 2023-07-17 14:56:24 by Fanny Dufresne. % Done: 0

• All parameters from linemodelsolve are under linemodelsolve.linemodel, which is kind of useless. We could suppress the '.linemodel' part

• In parameters file there are some names in camlcase, snakecase, in between etc, we could decide a given rule

• rename secondpasslcfittingmethod -> secondpass.fittingmethod ?