[Feature]: Add support for per-scenario seed configuration

[tsv1]

Summary:

Currently, the SeederPlugin allows for deterministic random behavior via global seeding options such as --seed and --fixed-seed. However, there is no flexibility for configuring seeds or the use_fixed_seed behavior at the scenario level. This feature request proposes the addition of a @seed decorator, which would allow users to set both a custom seed and the use_fixed_seed parameter for individual scenarios.

Proposed Solution:

Introduce a @seed decorator that supports both a custom seed and an optional use_fixed_seed parameter at the scenario level. This would provide flexibility for users to define:

1. A specific seed for individual scenarios.
2. Whether the seed should remain fixed across multiple executions of that scenario within the same test run.

This per-scenario configuration would override the global seed and use_fixed_seed settings for those specific scenarios.

The decorator would accept two parameters:

• seed: A string that specifies the seed for the scenario.
• use_fixed_seed: A boolean (optional) to indicate whether the seed should remain fixed for repeated runs of the scenario within the same test run.

Example Usage:

import vedro
from vedro import seed

@seed("custom-seed-123", use_fixed_seed=True)
class Scenario(vedro.Scenario):
    ...

In this example:

• The Scenario is seeded with "custom-seed-123", ensuring deterministic random behavior.
• The use_fixed_seed=True option ensures that the same seed will be used for each repetition of the scenario in a single test run, even if it's repeated multiple times.

If the use_fixed_seed parameter is not provided, it will default to the global setting, allowing flexibility without needing to redefine it for every scenario.