This PR modifies our reparse strategy for@type and@satisfies assertions. Previously, we'd generate anast.AsExpression orast.SatisfiesExpression containing clones of the target expression and type, and mark all of them asast.NodeFlagsReparsed. This had the unfortunate effect of "hiding" the target expression because it would now only occur in the AST as a reparsed node. With this PR, we still generate anast.AsExpression orast.SatisfiesExpression, but we no longer mark it as reparsed. We re-parent the target expression into the assertion node, but still clone the target type and mark it asast.NodeFlagsReparsed. So, the AST reflects a normalast.AsExpression orast.SatisfiesExpression with anExpression child that is the original expression andType child that is markedast.NodeFlagsReparsed. This flag on theType node makes it simple to detect the transformation, should that be necessary.

With this PR we have the nice property that reparsed nodes can consistently be ignored in AST walks.

The PR also contains:

• A panic that occurs ifast.GetOrCreateToken is called with a parent markedast.NodeFlagsReparsed. Tokens should never be created from reparsed nodes.
• The node visitor inaddRegionOutliningSpans is modified to skip over reparsed nodes.
• Fixed error spans on@satisfies assertions to be consistent with errors spans on@type assertions.

Fixes#2245.
Fixes#2289.
Fixes#2346.