{borrow,ptr}_as_ptr: don't lint inside proc-macros

[ada4a]

this could arguably be 2 separate PRs, but both of these were brought up in the same issue, so..

fixes #15398

• I'm a bit doubtful about the last commit -- see the message for my reasoning and do let me know whether it's right.

changelog: [borrow_as_ptr]: don't lint inside proc-macros
changelog: [ptr_as_ptr]: don't lint inside proc-macros

[rustbot]

r? @Jarcho

rustbot has assigned @Jarcho.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[Jarcho]

The last commit is not correct. is_from_proc_macro is actually broken and doesn't account for macro variables at all. I would just revert that change and leave a FIXME note in it's place.

[Jarcho]

Thank you. Can you just squash the last three commits down please.

[ada4a]

done!