Rename cfg_match! to cfg_select!

At [1] it was pointed out that `cfg_match!` syntax does not actually
align well with match syntax, which is a possible source of confusion.
The comment points out that usage is instead more similar to ecosystem
`select!` macros. Rename `cfg_match!` to `cfg_select!` to match this.

Tracking issue: https://github.com/rust-lang/rust/issues/115585

[1]: https://github.com/rust-lang/rust/issues/115585#issuecomment-2346307605

compiler/rustc_data_structures/src/flock.rs

@@ -4,7 +4,7 @@
 //! green/native threading. This is just a bare-bones enough solution for
 //! librustdoc, it is not production quality at all.
 
-cfg_match! {
+cfg_select! {
     target_os = "linux" => {
         mod linux;
         use linux as imp;

compiler/rustc_data_structures/src/lib.rs

@@ -19,7 +19,7 @@
 #![feature(ascii_char_variants)]
 #![feature(assert_matches)]
 #![feature(auto_traits)]
-#![feature(cfg_match)]
+#![feature(cfg_select)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(extend_one)]

compiler/rustc_data_structures/src/profiling.rs

@@ -860,7 +860,7 @@ fn get_thread_id() -> u32 {
 }
 
 // Memory reporting
-cfg_match! {
+cfg_select! {
     windows => {
         pub fn get_resident_set_size() -> Option<usize> {
             use windows::{