Improve Rename API

[clayellis]

Resolves #67

[JohnSundell]

@clayellis Do you think this is still an issue with Files 4.0+?

[clayellis]

@JohnSundell the surface area of the rename API didn't change between 3 and 4 — so I think the original motivations from #67 remain. However, I wasn't the one who brought up the issue, I just wrote the "fix", so I'm not super opinionated. Though, I do think this revision is a little more explicit and helps the user clarify their intent.

[maximkrouk]

#124 is kinda related in terms of what name and what extension is, I suppose that for the hidden files the current PR implementation may treat name as an empty string

Example
.swiftlint -> (change name to .swiftformat) -> .swiftformat.swiftlint
.swiftlint -> (change extension to yml) -> .yml
Instead of
.swiftlint -> (change name to .swiftformat) -> .swiftformat
.swiftlint -> (change extension to yml) -> -> .swiftlint.yml

Btw I think that getting the name and the extension should probably work like this 🤔
.swiftlint -> (name, extension) -> (".swiftlint", "")
.swiftlint.yml -> (name, extension) -> (".swiftlint", "yml")
Maybe even (but the previous one is frankly better)
.swiftlint -> (name, extension) -> (".swiftlint", "swiftlint")
.swiftlint.yml -> (name, extension) -> (".swiftlint", "yml")

[clayellis]

Closing, since it's been a few years without activity.