fix: handle SelfParam better in "Inline call"

[roife]

fix #15470.

The current inline_call directly translates &self into let ref this = ...; and &mut self into let ref mut this = ...;. However, it does not handle some complex scenarios.

This PR addresses the following transformations (assuming the receiving object is obj):

• self: let this = obj
• mut self: let mut this = obj
• &self: let this = &obj
• &mut self
  • If obj is let mut obj = ..., use a mutable reference: let this = &mut obj
  • If obj is let obj = &mut ...;, perform a reborrow: let this = &mut *obj

[Veykril]

@bors r+

[bors]

📌 Commit 920e99a has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit 920e99a with merge f4fec4f...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing f4fec4f to master...