add std repeat command to replace "foo" * 3 (#10339)

related to
- https://github.com/nushell/nushell/issues/10233
- https://github.com/nushell/nushell/pull/10293
- https://github.com/nushell/nushell/pull/10292

inspired by @kubouch 

# Description
this PR adds a `repeat` command to the standard library

# User-Facing Changes
a new `repeat` command in `std`
```nushell
repeat anything a bunch of times, yielding a list of *n* times the input

# Examples
    repeat a string
    > "foo" | std repeat 3 | str join
    "foofoofoo"

Usage:
  > repeat <n>

Flags:
  -h, --help - Display the help message for this command

Parameters:
  n <int>: the number of repetitions, must be positive

Input/output types:
  ╭───┬───────┬───────────╮
  │ # │ input │  output   │
  ├───┼───────┼───────────┤
  │ 0 │ any   │ list<any> │
  ╰───┴───────┴───────────╯
```

# Tests + Formatting
a new test called `repeat_things` in `test_std.nu`

# After Submitting

crates/nu-std/tests/test_std.nu

@@ -44,3 +44,14 @@ def path_add [] {
 def banner [] {
     std assert ((std banner | lines | length) == 15)
 }
+
+#[test]
+def repeat_things [] {
+    std assert error { "foo" | std repeat -1 }
+
+    for x in ["foo", [1 2], {a: 1}] {
+        std assert equal ($x | std repeat 0) []
+        std assert equal ($x | std repeat 1) [$x]
+        std assert equal ($x | std repeat 2) [$x $x]
+    }
+}