[flang] Support coarrays in name resolution

[flang] Support coarrays in name resolution

A coarray is represented as a `Symbol` with `ObjectEntityDetails` that
has a non-empty coshape. The coshape is represented using the same type
(`ArrayShape`) as the shape is, so the fact that it is a coshape is
determined from context.

Move code for analyzing shapes to `resolve-names-utils.cc` and
generalize it for coshapes.

In `symbol.cc` add dumping of coshapes. Simplify some of the functions
by adding some `Dump*` functions to handle common cases.

In `mod-file.cc` generalize the code for writing shapes to also write
coshapes. Fix a bug in `PutShapeSpec()`.

Original-commit: flang-compiler/f18@9d2482c40c78cad55701a9cbc52a2294cae94d44
Reviewed-on: https://github.com/flang-compiler/f18/pull/384
Tree-same-pre-rewrite: false