fix: deal with the race between duplication and on_checkpoint_timer

[ninsmiracle]

What problem does this PR solve?

#2211

What is changed and how does it work?

add lock when remove_all_duplication.
We can see src/replica/duplication/replica_duplicator_manager.h, there are code comments like this

    // avoid thread conflict between replica::on_checkpoint_timer and
    // duplication_sync_timer.
    mutable zlock _lock;

So we need to perfect this lock's usage.

Checklist

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

How this PR work?

Possible conflict locations with on_checkpoint_timer:

void replica::on_checkpoint_timer()
{
    if (_private_log) {
    mutation_log_ptr plog = _private_log;

    decree last_durable_decree = _app->last_durable_decree();
    // RACE PROBLEM!!!
    decree min_confirmed_decree = _duplication_mgr->min_confirmed_decree();
    decree cleanable_decree = last_durable_decree;
    int64_t valid_start_offset = _app->init_info().init_offset_in_private_log;
    /// ...

    }
/// ...
}


decree replica_duplicator_manager::min_confirmed_decree() const
{
    zauto_lock l(_lock);

    decree min_decree = invalid_decree;
    if (_replica->status() == partition_status::PS_PRIMARY) {
        // HERE
        for (auto &kv : _duplications) {
            const duplication_progress &p = kv.second->progress();
            if (min_decree == invalid_decree) {
                min_decree = p.confirmed_decree;
            } else {
                min_decree = std::min(min_decree, p.confirmed_decree);
            }
        }
    } else if (_primary_confirmed_decree > 0) {
        // if the replica is not primary, use the latest known (from primary)
        // confirmed_decree instead.
        min_decree = _primary_confirmed_decree;
    }
    return min_decree;
}