Add simple Else conditions to If Conversion (#77728)

Add simple Else conditions to If Conversion (#77728)

* Add simple Else conditions to If Conversion

For example:
if (x < 7) { a = 5; } else { a = 9; }
a = (cond) ? b : c;

The else condition must write to the same variable as the then
statement.

* Move phase and stop updating ssa

* Wrap JitConfig access

* Add GT_RETURN else cases

* Add test cases with verification checks

* Ensure single only operation condition checks are used

* Remove empty line

* Use DOTNET_ instead of COMPlus_

* Move JitDoIfConversion check

* Move if conversion into it's own file

* Always invert condition

* Rename IfConvertMergeBlocks

* Use gtGetOp1()

* Expand tests

* Add operation type assert

* Allow nested SELECT nodes

* Fix condition directions