Rename random decimal to random float (#10320)

# Description
Similar to #9979

# User-Facing Changes
`random decimal` will now raise a warning and can be removed in an
upcoming release.

New command is named `random float`

# Tests + Formatting
Tests updated and improved.

crates/nu-command/src/default_context.rs

@@ -368,6 +368,7 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             RandomChars,
             RandomDecimal,
             RandomDice,
+            RandomFloat,
             RandomInteger,
             RandomUuid,
         };