[flang] Move various Instantiate functions to tools.cc

[flang] Move various Instantiate functions to tools.cc

Move these functions from scope.cc, symbol.cc, type.cc into tools.cc:
  Scope::FindOrInstantiateDerivedType
  Scope::InstantiateDerivedType
  Scope::InstantiateIntrinsicType
  Symbol::Instantiate
  DerivedTypeSpec::ProcessParameterExpressions
  DerivedTypeSpec::Instantiate

This eliminates some dependencies in these files on SemanticsContext,
FoldingContext, etc.

It also allows three of the functions to be private to tools.cc
because they are only called from the others.

Original-commit: flang-compiler/f18@48c6efbf95390446fa10ca61b3e7f6b7db6c836d
Reviewed-on: https://github.com/flang-compiler/f18/pull/559
Tree-same-pre-rewrite: false