Include the source location in Closure names (#13550)

* Include the source location in Closure names

This change makes stack traces involving Closures, especially multiple
diffe

Include the source location in Closure names (#13550)

* Include the source location in Closure names

This change makes stack traces involving Closures, especially multiple
different Closures, much more useful, because it's more easily visible *which*
closure was called for a given stack frame.

The implementation is similar to that of anonymous classes which already
include the file name and line number within their generated classname.

* Update scripts/dev/bless_tests.php for closure naming

* Adjust existing tests for closure naming

* Adjust tests for closure naming that were not caught locally

* Drop the namespace from closure names

This is redundant with the included filename.

* Include filename and line number as separate keys in Closure debug info

* Fix test

* Fix test

* Include the surrounding class and function name in closure names

* Fix test

* Relax test expecations

* Fix tests after merge

* NEWS / UPGRADING

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