program error: use unambigious globs

[buffalojoec]

Problem

When annotating an error enum with [spl_program_error], the generated
trait implementations are using solana_program directly, which might cause
conflicts with the program_error crate's version of solana_program and
the program's version.

error[E0659]: `solana_program` is ambiguous
 --> /Users/joesol/.cargo/git/checkouts/address-lookup-table-b4ff4f65bda84997/11a0b41/program/src/error.rs:5:1
  |
5 | #[spl_program_error]
  | ^^^^^^^^^^^^^^^^^^^^ ambiguous name
  |
  = note: ambiguous because of a conflict between a name from a glob import and an outer scope during import or macro resolution
  = note: `solana_program` could refer to a crate passed with `--extern`
  = help: use `::solana_program` to refer to this crate unambiguously

Summary of Changes

Use unambiguous imports to let the Rust compiler decide which version to use!