Fix storage expansion in pallet section (#6023)

fixes #5320 @sam0x17 @gupnik 

# Description

The issue could be confirmed with the added example. The cause is for
macro hygiene, `entries` in the `#( #entries_builder )*` expansion won't
be able to reference the `entries` defined outside. The solution here is
to allow the reference to be passed into the expansion with closure.

Or we could just switch to the unhygienic span with `quote::quote!`
instead such that `entries` will resolve to the "outer" definition.