fix: require equals for icons values

[cyphercodes]

Description

Require --icons optional values to use = (for example --icons=always) so a bare --icons does not consume the following positional file argument. Updated the parser/unit tests and powertest expectations for the help text and explicit icon modes.

Fixes #1864

How Has This Been Tested?

• cargo fmt --check
• cargo test
• ./target/debug/eza --icons src/options/parser.rs
• ./target/debug/eza --icons=always src/options/parser.rs

[AvianAnalyst]

Hey! Just wanted to chime in, --icons isn't the only argument with this bug. --hyperlink was my introduction to it, and after running through the man page and checking options, here's the full list:
--absolute
--classify (and -F)
--colo(u)r
--icons
--hyperlink

Note: --code works, but breaks completion, (at least in fish)