Refactor ansi stripping into nu-utils functions (#6966)

Allows use of slightly optimized variants that check if they have to use
the heavier vte parser. Tries to avoid unnnecessary allocations. Initial
performance characteristics proven out in #4378.

Also reduces boilerplate with right-ward drift.

crates/nu-utils/src/lib.rs

@@ -1,3 +1,4 @@
+mod deansi;
 pub mod locale;
 pub mod utils;
 
@@ -6,3 +7,7 @@ pub use utils::{
     enable_vt_processing, get_default_config, get_default_env, get_ls_colors,
     stderr_write_all_and_flush, stdout_write_all_and_flush,
 };
+
+pub use deansi::{
+    strip_ansi_likely, strip_ansi_string_likely, strip_ansi_string_unlikely, strip_ansi_unlikely,
+};