feat: Separate pause and unpause roles in Pausable plugin

[r-near]

Replaces the single manager_roles attribute with separate pause_roles and unpause_roles attributes in the Pausable plugin. This enables assigning different permissions for pausing and unpausing features.

Implementation

• Modified pausable.rs trait and implementation to support separate role specifications
• Updated test contracts and tests
• Added migration documentation and CHANGELOG entry

Usage

// Before
#[pausable(manager_roles(Role::PauseManager))]

// After
#[pausable(
    pause_roles(Role::PauseManager),
    unpause_roles(Role::UnpauseManager)
)]

Impact

Breaking change that requires code updates when upgrading. This enables more granular security policies, particularly in scenarios where emergency pausing should be available to more accounts than unpausing.

• Closes Split pause and unpause roles #151
• Closes Pausable: add pause & unpause roles #124

[mitinarseny]

You should never remove a variant or add one more in the middle of enums with #[derive(AccessControlRole)], since it uses bitflags to store permissions for each AccountId.
Please, fix the migration guide.

[karim-en]

You should never remove a variant or add one more in the middle of enums with #[derive(AccessControlRole)], since it uses bitflags to store permissions for each AccountId.
Please, fix the migration guide.

@r-near can you please also add a migration test for this.

[karim-en]

cc @r-near

[r-near]

@karim-en PR here: #163