Assign PROGRAM_FILE earlier (#22092)
* Assign PROGRAM_FILE earlier
I discovered a use case where it would be nice to be able to access
`PROGRAM_FILE` while within the .juliarc.jl. The global variable is
now assigned and available within `--load` file or the .juliarc.jl.
Additionally, PROGRAM_FILE is now a constant.
* Add to NEWS
[ci skip]
* Test startup-file and PROGRAM_FILE
* Modify user home properly on Windows
* Style correction and remove escape function
* Expand arguments tests to include the startup-file
* Refactor PROGRAM_FILE tests
