docs: document generic and common enum types

[GarmashAlex]

Filled in the previously empty enum-types.adoc section with concrete documentation for advanced enum usage in Cairo. It explains how to define and use generic enums, shows how matching on generic enums works, and introduces common patterns such as Option for optional values and Result<T, E> for success/error flows. The goal is to complement the basic
enums.adoc page and give readers practical guidance on modeling data with reusable enum abstractions.

[reviewable-StarkWare]

This change is 

[orizi]

Reviewable status: 0 of 1 files reviewed, 6 unresolved discussions (waiting on @GarmashAlex)

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docs/reference/src/components/cairo/modules/language_constructs/pages/enum-types.adoc line 21 at r1 (raw file):

        Some: T,
        None: (),
    }

Suggestion:

        Some: T,
        None,
    }

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docs/reference/src/components/cairo/modules/language_constructs/pages/enum-types.adoc line 31 at r1 (raw file):

[source,cairo]
----
use option::Option;

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docs/reference/src/components/cairo/modules/language_constructs/pages/enum-types.adoc line 49 at r1 (raw file):

[source,cairo]
----
    enum Pair<T, U> {

weird example.

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docs/reference/src/components/cairo/modules/language_constructs/pages/enum-types.adoc line 64 at r1 (raw file):

use option::Option;

fn unwrap_or_default(x: Option<u32>, default: u32) -> u32 {

Suggestion:

fn unwrap_or_default(x: Option<u32>, default: u32) -> u32 {

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docs/reference/src/components/cairo/modules/language_constructs/pages/enum-types.adoc line 68 at r1 (raw file):

        Option::Some(value) => value,
        Option::None(()) => default,
    }

Suggestion:

    match x {
        Some(value) => value,
        None(()) => default,
    }

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docs/reference/src/components/cairo/modules/language_constructs/pages/enum-types.adoc line 81 at r1 (raw file):

standard patterns.

=== Option

all previous examples should not be related to options - if you specifically talk about it now.

[orizi]

No response.

Closing.