ambiguity during lookup when there are multiple public or inlinalbe
package decls in public interfaces. This PR adds a package name to
public swiftinterface and lets typecheck look up the package name
to narrow down the scope of access to package decls from an external
module.
Resolves rdar://117699160
Package decls are only printed in interface files if they are inlinable
(@usableFromInline, @inlinable, @_alwaysEmitIntoClient). They could be
referenced by a module outside of its defining module that belong to the same
package determined by the `package-name` flag. However, the flag is only in
.swiftmodule and .private.swiftinterface, thus type checking references of
inlinable package symbols in public interfaces fails due to the missing flag.
Instead of adding the package-name flag to the public interfaces, which
could raise a security concern, this PR grants access to such cases.
Resolves rdar://116142791