Update E0207 to use struct_span_err, add span_label

[shantanuraj]

Fixes #35302 part of #35233

r? @jonathandturner

[rust-highfive]

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[sophiajt]

Thanks for the PR!

You'll also need to update the corresponding unit tests. You can find them by running git grep E0207

jturner-23759:rust jturner$ git grep E0207
...
src/test/compile-fail/E0207.rs:impl<T: Default> Foo { //~ ERROR E0207
src/test/compile-fail/impl-unused-rps-in-assoc-type.rs:impl<'a> Fun for Holder { //~ ERROR E0207
src/test/compile-fail/issue-22886.rs:impl<'a> Iterator for Newtype { //~ ERROR E0207
src/test/compile-fail/issue-35139.rs:impl<'a> MethodType for MTFn { //~ ERROR E0207

[sophiajt]

Looks good!

@bors r+ rollup

[bors]

📌 Commit 58b618e has been approved by jonathandturner

[shantanuraj]

Awesome, thanks for the insight @jonathandturner the unit tests seemed a little challenging at first, then I looked into another commit GuillaumeGomez@158597f which gave some insight about adding them.