Refactor assigning_clones

[Jarcho]

Short list of changes:

• Inline and simplify extract_call
• Inline is_ok_to_suggest
• Inline skip_drop_block
• Check the HIR tree before the macro check
• Don't call outer_expn_data
• Use find instead of a loop in clone_source_borrows_from_dest

changelog: none

[rustbot]

r? @Manishearth

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[Manishearth]

@bors r+

[bors]

📌 Commit d9ab0a7 has been approved by Manishearth

It is now in the queue for this repository.

[bors]

⌛ Testing commit d9ab0a7 with merge 058e6ea...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Manishearth
Pushing 058e6ea to master...

[Kobzol]

@Jarcho I'm curious, do you really find the new version to be more readable? Before, it was quite easy for me to follow the logic of the lint, because it was quite simple sequential code. Now the main selection logic is in a single expression that has 13 && operators... I find it very difficult to make sense of this.