Graceful error recovery for files with no read permission

[NikitaRevenco]

If you try to open a file which the user can't read, helix will throw an error:

$ touch file
$ chmod -r file
$ hx file
Error: unable to start Helix

Caused by:
    Permission denied (os error 13)

But we get the same error if we try to open multiple files, even if some of them are readable

$ touch file{1..10}
$ chmod -r file1
$ hx file{1..10}
Error: unable to start Helix

Caused by:
    Permission denied (os error 13)

Desirable outcome

If you open multiple files but some of them can't be read, Helix should open the ones that can be, and set a message which files failed to open

I'm thinking that a status message should be set like this:

Opened 10 files, but couldn't open 4:
- abc.txt
- xyz.txt
- 123.txt
- 111.txt

Currently the status message is limited to a single one. When #12241 is merged this can be implemented

[kirawi]

helix/helix-stdx/src/faccess.rs

Line 466 in ea17b9e

pub fn readonly(p: &Path) -> bool {

should be used. I'm surprised it wasn't already.