Update deprecation warnings (#15867)

# Description
- Use #15770 to
  - improve `get --sensitive` deprecation warning
  - add deprecation warning for `filter`
- refactor `filter` to use `where` as its implementation
- replace usages of `filter` with `where` in `std`

# User-Facing Changes
- `get --sensitive` will raise a warning only once, during parsing
whereas before it was raised during runtime for each usage.
- using `filter` will raise a deprecation warning, once

# Tests + Formatting
No existing test broke or required tweaking. Additional tests covering
this case was added.
- 🟢 toolkit fmt
- 🟢 toolkit clippy
- 🟢 toolkit test
- 🟢 toolkit test stdlib

# After Submitting
N/A

---------

Co-authored-by: Bahex <17417311+Bahex@users.noreply.github.com>

crates/nu-std/std/xml/mod.nu

@@ -62,7 +62,7 @@ def xupdate-string-step [ step: string rest: list updater: closure ] {
     let input = $in
 
     # Get a list of elements to be updated and their indices
-    let to_update = ($input.content | enumerate | filter {|it|
+    let to_update = ($input.content | enumerate | where {|it|
         let item = $it.item
         $step == '*' or $item.tag == $step
     })