fix sub-command merges directives accepting lists of values into super-long lines

[Gedochao]

Version(s)
d8b3313 / 1.5.4-94-gd8b33133f-SNAPSHOT

Describe the bug
When running the fix sub-command's built-in rules, directives from multiple files are migrated into the project.scala configuration file.
When a directive key accepting multiple values (i.e. //> using dep) is repeated across the project, Scala CLI will merge it into a single directive.
The resulting directive can then be unreasonably long.

To Reproduce
given

// file1.scala
//> using dep com.lihaoyi::os-lib:0.9.1

// file2.scala
//> using dep com.lihaoyi::pprint:0.8.0

//file3.scala
//> using  dep org.scala-lang::scala3-compiler:3.6.2

the resulting project.scala looks like this:

// Main
//> using dependency "com.lihaoyi::os-lib:0.9.1"  "com.lihaoyi::pprint:0.8.0" "org.scala-lang::scala3-compiler:3.6.2"

Expected behaviour
Directives in project.scala should hold to a reasonable line length after migrating with fix.