Feature Request: Support pretty-printing collection types

Dear all,

I would like to see `terraform fmt` support pretty-printing collection types. Currently I observe that internal `terraform fmt` code runs format passes on _fixed_ lines (please see [format.go](https://github.com/hashicorp/hcl/blob/main/hclwrite/format.go#L27C1-L27C33)). But I hope it can help me format variables of collection types (_list_, _set_, _map_), for instance

```hcl
variable "example_set" {
type = set(string)
default = ["foo", "bar", "dog", "cat", "jojo"]
}

# reformatted to =========================>

variable "example_set" {
type = set(string)
default = [
"foo",
"bar",
"dog",
"cat",
"jojo"
]
}
```

To my understanding, implementing this feature requires replacing the current `[]formatLine` with other data strucutres like linked lists to allow flexible line insertions.

I hope you can put my feature request on your radar! If you don't mind, I'm also willing to implement it if you agree.

Best regards,

Xulei

Start with hclwrite/format.go, especially the current format passes and []formatLine structure used by terraform fmt. Compare the existing formatting behavior with the collection example in the issue; done means list, set, and map values can be formatted across multiple lines as shown.

Written by the indexing model from the issue text.