Removes redundant parentheses

[0x7CFE]

Recent nightly contains lint for redundant parentheses in expressions, that typically looks like this:

warning: unnecessary parentheses around function argument
   --> util/rlp/src/untrusted_rlp.rs:279:43
    |
279 |             result = UntrustedRlp::consume(result, (i.header_len + i.value_len))?;
    |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove these parentheses
    |
    = note: #[warn(unused_parens)] on by default

Entries in normal sources were modified accordingly. However, there are a lot of generated files, where n-tuple is returned as Ok part of a function's Result. In case of 1-tuple it looks like Ok((x)) which makes rustc nervous.

In order to calm the compiler down, I've added #![allow(unused_parens)] in generated modules and simplified the expressions in normal code (where applicable).

Also, updater/src/operations.rs seems to be autogenerated, but since it was in the repo, I decided to fix it by hand as well.

[andresilva]

Long-term maybe we should fix the generators so that we don't have to allow unused_parens.

[tomusdrw]

I think @debris is getting rid of generated code in general, so it shouldn't be an issue with any new code.