Improve fatal err msg (#24390)

Improve fatal err msg (#24390)

* Improve fatal err msg

* Match SO format

* a

* Remove dead define

* More adjustments to ex msg

* And PAL

* Remove special case for SOE

* Remove excess Debug.Assert newline

* Remove excess newline

* typo

* New format

* Remove DebugProvider redundancy

* Adjustments

* Remove preceding newline

* Make other SOE and OOM consistent

* Tidy up assertion msg

* Fix missing newline after inner exception divider

* CR when no inner exception

* ToString never CR terminated

* disable corefx tests temporarily