Program name ($0) relative paths should not be expanded

Describe the bug

sh and sh-like shells don't expand relative paths when executing a program or script, but nushell does. This behaviour in nushell break assumes by some scripts, causing them to fail.

To demonstrate, if I create a script to print the program name it was called with:

$ echo "#!/bin/sh\necho $0" o> test.sh
$ chmod +x test.sh

Then if I execute it via a relative path in the current directory, the results are different between nushell and sh:

~/tmp $ cat test.sh
#!/bin/sh
echo $0

 ~/tmp $ ./test.sh
/home/user/tmp/./test.sh

~/tmp $ sh -c './test.sh'
./test.sh

How to reproduce

1. create an executable file that will print the name of the program being executed (eg. $0 in bash, or $PROGRAM_NAME in ruby):

$ echo "#!/bin/sh\necho $0" o> test.sh
$ chmod +x test.sh

2. execute the file from nushell using a relative path, and note that the path is expanded.

$ ./test.sh
/home/user/tmp/./test.sh

Expected behavior

The path should not be expanded. It should remain as given by the user, to be consistent with other shells, and not break assumptions that scripts have.

Configuration

NA - same results with nu -n

Start by reproducing the behavior described with an executable script run through nushell, comparing its program name with sh -c './test.sh'. Trace the relative-path execution entry point and add coverage showing that the user-supplied relative path is preserved; done means ./test.sh is reported as ./test.sh rather than an expanded absolute path.