target_link_libraries: Restore transitive out-of-dir linking

Refactoring in commit 7f506b95 (cmGeneratorTarget: Refactor link item
lookup, 2021-05-26, v3.21.0-rc1~103^2~4) accidentally dropped the
persistent lookup scope tracking across multiple items that was added by
commit f0e67da0 (target_link_libraries: Fix out-of-dir linking of a
list of targets, 2020-01-14, v3.17.0-rc1~149^2).  This broke a
transitive out-of-dir linking case not covered by our test suite.
Restore the scope tracking and add a test case.

Fixes: #22363