Split `possible_missing_else` from `suspicious_else_formatting` (#15317)

This has always been one lint (added in rust-lang/rust-clippy#720), but
the two cases are also quite distinct.

changelog: Split `possible_missing_else` from
`suspicious_else_formatting`

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### Summary Notes

-
[Feature-freeze](https://github.com/rust-lang/rust-clippy/pull/15317#issuecomment-3094592022)
by [github-actions[bot]](https://github.com/github-actions[bot])

*Managed by `@rustbot`—see
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2 files changed, 9 insertions, 7 deletions

diff --git a/tests/ui/suspicious_else_formatting.rs b/tests/ui/suspicious_else_formatting.rs
index 28a3b551116..072e7b27b0d 100644
--- a/tests/ui/suspicious_else_formatting.rs
+++ b/tests/ui/suspicious_else_formatting.rs
@@ -1,6 +1,6 @@
 //@aux-build:proc_macro_suspicious_else_formatting.rs
 
-#![warn(clippy::suspicious_else_formatting)]
+#![warn(clippy::suspicious_else_formatting, clippy::possible_missing_else)]
 #![allow(
     clippy::if_same_then_else,
     clippy::let_unit_value,
@@ -20,12 +20,12 @@ fn main() {
     // weird `else` formatting:
     if foo() {
     } {
-    //~^ suspicious_else_formatting
+    //~^ possible_missing_else
     }
 
     if foo() {
     } if foo() {
-    //~^ suspicious_else_formatting
+    //~^ possible_missing_else
     }
 
     let _ = { // if as the last expression
@@ -33,7 +33,7 @@ fn main() {
 
         if foo() {
         } if foo() {
-        //~^ suspicious_else_formatting
+        //~^ possible_missing_else
         }
         else {
         }
@@ -42,7 +42,7 @@ fn main() {
     let _ = { // if in the middle of a block
         if foo() {
         } if foo() {
-        //~^ suspicious_else_formatting
+        //~^ possible_missing_else
         }
         else {
         }
diff --git a/tests/ui/suspicious_else_formatting.stderr b/tests/ui/suspicious_else_formatting.stderr
index affd20b22d9..04555c6edbd 100644
--- a/tests/ui/suspicious_else_formatting.stderr
+++ b/tests/ui/suspicious_else_formatting.stderr
@@ -5,8 +5,8 @@ LL |     } {
    |      ^
    |
    = note: to remove this lint, add the missing `else` or add a new line before the next block
-   = note: `-D clippy::suspicious-else-formatting` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::suspicious_else_formatting)]`
+   = note: `-D clippy::possible-missing-else` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::possible_missing_else)]`
 
 error: this looks like an `else if` but the `else` is missing
   --> tests/ui/suspicious_else_formatting.rs:27:6
@@ -41,6 +41,8 @@ LL | |     {
    | |____^
    |
    = note: to remove this lint, remove the `else` or remove the new line between `else` and `{..}`
+   = note: `-D clippy::suspicious-else-formatting` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::suspicious_else_formatting)]`
 
 error: this is an `else if` but the formatting might hide it
   --> tests/ui/suspicious_else_formatting.rs:67:6