Expand completion support for language server (chapel-lang#25991)

This PR expands upon our existing completion support to be location
specific. Prior to this PR, only the module level scope was used to
provide completion symbols. This PR changes that, so that visible
symbols are computed based upon the users cursor.


With this PR, users will get an auto-complete suggestion of 'myVariable'
when 'myV' is typed.
```chapel
record myRecord {
  var  myVariable = 1;
  proc foo() {
    myV
  }
}
```

Implementation details

This PR uses the fact that the FileInfo visits nodes in order when
building segments. So in the above example, the scope for `myRecord` is
visited before `foo`. As each scope is entered, we keep track of the
location, its Scope object, and the parent scopes. This is precomputed
before a user ever requests a completion, so that when that occurs it is
just a simple lookup.

[Reviewed by @DanilaFe]

tools/chapel-py/src/method-tables/uast-methods.h

@@ -66,6 +66,8 @@ CLASS_BEGIN(AstNode)
                std::optional<ScopeObject*>,
 
                return ScopeObject::tryCreate(contextObject, resolution::scopeForId(context, node->id())))
+  PLAIN_GETTER(AstNode, creates_scope, "Returns true if this AST node creates a scope",
+               bool, return chpl::resolution::createsScope(node->tag()))
   PLAIN_GETTER(AstNode, type, "Get the type of this AST node, as a 3-tuple of (kind, type, param).",
                std::optional<QualifiedTypeTuple>,