Core: Fix reference to nested column added to map/list in same transaction

[huan233usc]

Problem

SchemaUpdate records a column added in the current transaction in addedNameToId, keyed by the column's name, so that a later operation in the same transaction (updateColumn, updateColumnDoc, requireColumn, makeColumnOptional, or a move) can resolve the not-yet-committed column.

For a column added into a map value struct or a list element struct, internalAddColumn builds the key from the parent's canonical name via schema.findColumnName(parentId), which includes the synthetic value / element segment:

fullName = schema.findColumnName(parentId) + "." + name;   // e.g. "locations.value.alt"
addedNameToId.put(caseSensitivityAwareName(fullName), newId);

But callers address such a column by its user-facing short name (locations.alt, points.z) — the form the schema's own name index exposes for map value / list element structs. findForUpdate first tries findField(name) (which can't see the pending column) and then falls back to addedNameToId.get(name), so the lookup misses and the operation fails with Cannot update missing column: locations.alt.

Only the full canonical path (locations.value.alt) works today, which is not the name users write.

Example

new SchemaUpdate(schema, lastColumnId)
    .addColumn("locations", "alt", Types.FloatType.get()) // into a map<..., struct> value
    .updateColumnDoc("locations.alt", "altitude")          // -> IllegalArgumentException today
    .apply();

Fix

Also index the user-facing short name in addedNameToId for nested adds, so the shorthand resolves. This mirrors how the schema's own IndexByName tracks both the full and short paths (dropping value/element for structs nested in a map value / list element). Top-level and plain-struct adds are unaffected because their short name equals the full name.

Tests

Added TestSchemaUpdate.testUpdateColumnAddedToMapValueOrListElementInSameTransaction: adds a field into a map value struct and a list element struct, then references each by its short name (locations.alt, points.z) in the same transaction. It fails before the change with Cannot update missing column and passes after. The full TestSchemaUpdate suite remains green.

[ebyhr]

This comment is too verbose. I suggest simplifying it. The same goes for the new tests.

[huan233usc]

Thanks, simplified a bit