Migrate away from `if_chain` in nightly code

[smoelius]

Following Clippy's lead: rust-lang/rust-clippy#11750

Note that this only applies to code compile with nightly toolchains (driver, dylint_linting, and example lints).

• examples/experimental/derive_opportunity/src/lib.rs
• examples/general/crate_wide_allow/src/lib.rs
• examples/general/env_cargo_path/src/lib.rs
• examples/general/incorrect_matches_operation/src/lib.rs
• examples/general/non_local_effect_before_error_return/src/lib.rs
• examples/general/non_local_effect_before_error_return/src/visit_error_paths.rs
• examples/general/non_thread_safe_call_in_test/src/late.rs
• examples/general/non_thread_safe_call_in_test/src/pre_expansion.rs
• examples/general/wrong_serialize_struct_arg/src/lib.rs
• examples/restriction/collapsible_unwrap/src/lib.rs
• examples/restriction/const_path_join/src/lib.rs
• examples/restriction/env_literal/src/lib.rs
• examples/restriction/inconsistent_qualification/src/lib.rs
• examples/restriction/misleading_variable_name/src/lib.rs
• examples/restriction/overscoped_allow/src/lib.rs
• examples/restriction/question_mark_in_expression/src/lib.rs
• examples/restriction/ref_aware_redundant_closure_for_method_calls/src/lib.rs
• examples/restriction/suboptimal_pattern/src/lib.rs
• examples/restriction/try_io_result/src/lib.rs
• examples/supplementary/commented_code/src/lib.rs
• examples/supplementary/redundant_reference/src/lib.rs
• examples/supplementary/unnamed_constant/src/lib.rs
• examples/supplementary/unnecessary_borrow_mut/src/lib.rs
• examples/supplementary/unnecessary_conversion_for_trait/src/check_inherents.rs
• examples/supplementary/unnecessary_conversion_for_trait/src/lib.rs