Adjust signatures for cellpath access of tables (#9778)

# Description
Reallow the commands that take cellpaths as rest parameters to operate
on table input data.

Went through all commands returned by

```
scope commands |
  filter { |cmd| $cmd.signatures |
    values |
    any {|sig| $sig |
      any {|$sig| $sig.parameter_type == rest and $sig.syntax_shape ==
cellpath }
    }
  } | get name
```

Only exception to that was `is-empty` that returns a bool.
# User-Facing Changes
Same table operations as in `0.82` should still be possible
Mitigates effects of #9680

crates/nu-command/src/strings/encode_decode/decode_base64.rs

@@ -26,6 +26,7 @@ impl Command for DecodeBase64 {
                     Type::List(Box::new(Type::String)),
                     Type::List(Box::new(Type::Binary)),
                 ),
+                (Type::Table(vec![]), Type::Table(vec![])),
             ])
             .vectorizes_over_list(true)
             .allow_variants_without_examples(true)

crates/nu-command/src/strings/encode_decode/encode_base64.rs

@@ -32,6 +32,7 @@ impl Command for EncodeBase64 {
                     Type::List(Box::new(Type::Any)),
                     Type::List(Box::new(Type::String)),
                 ),
+                (Type::Table(vec![]), Type::Table(vec![])),
             ])
             .vectorizes_over_list(true)
             .allow_variants_without_examples(true)