Auto merge of #12765 - yusufraji:while-float, r=llogiq

Add new lint `while_float`

This PR adds a nursery lint that checks for while loops comparing floating point values.

changelog:
```
changelog: [`while_float`]: Checks for while loops comparing floating point values.
```

Fixes #758

tests/ui/while_float.rs

@@ -0,0 +1,14 @@
+#[deny(clippy::while_float)]
+fn main() {
+    let mut x = 0.0_f32;
+    while x < 42.0_f32 {
+        x += 0.5;
+    }
+    while x < 42.0 {
+        x += 1.0;
+    }
+    let mut x = 0;
+    while x < 42 {
+        x += 1;
+    }
+}

tests/ui/while_float.stderr

@@ -0,0 +1,20 @@
+error: while condition comparing floats
+  --> tests/ui/while_float.rs:4:11
+   |
+LL |     while x < 42.0_f32 {
+   |           ^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> tests/ui/while_float.rs:1:8
+   |
+LL | #[deny(clippy::while_float)]
+   |        ^^^^^^^^^^^^^^^^^^^
+
+error: while condition comparing floats
+  --> tests/ui/while_float.rs:7:11
+   |
+LL |     while x < 42.0 {
+   |           ^^^^^^^^
+
+error: aborting due to 2 previous errors
+