v2: Add new prior distributions

[dweindl]

See PEtab-dev/PEtab#595

• Update petab.v2.core.Parameter to include the prior distribution
  -> v2: Adapt models to changes in prior distributions #378
• Add new Distribution classes (requires Implement proper truncation for prior distributions #335)
  -> v2: Additional probability distributions #377
• update linter: valid distributions, correct number of parameters, ...
• v1->v2 conversion
  -> v1->v2: Update priors #379
• startpoint sampling via Problem
  -> v2: Startpoint sampling #380