Fix panic with unpinning pruned blocks

[tomaka]

Fixes a panic introduced in #2373

Imagine the following situation:
Block A has two children: block B and block C. The latest finalized block is currently block A. All three blocks are pinned.

Now, imagine that block B gets finalized. Block A, B, and C all stay pinned. The number of pinned blocks remaining is decreased by 1.

When the user then unpins block C, we check height(block_C) <= height(current_finalized_block), which returns true, and we add 1 to the number of pinned blocks remaining.
When the user then unpins block A, the same happens, and we add 1 again to the number of pinned blocks remaining.

This leads to an overflow when that number of pinned blocks is usize::max_value().

This PR fixes this problem by tracking in pinned_blocks whether the block counts towards the limit.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
        +726 ┊ alloc::collections::btree::remove::<impl alloc::collections::btree::node::Handle<alloc::collections::btree::node::NodeRef<alloc::collections::btree::node::marker::Mut,K,V,alloc::collections::btree::node::marker::Leaf>,alloc::collections::btree::node::marker::KV>>::remove_leaf_kv::h1d96892f0412a914
        -726 ┊ alloc::collections::btree::remove::<impl alloc::collections::btree::node::Handle<alloc::collections::btree::node::NodeRef<alloc::collections::btree::node::marker::Mut,K,V,alloc::collections::btree::node::marker::Leaf>,alloc::collections::btree::node::marker::KV>>::remove_leaf_kv::h657e6722127b262a
        -682 ┊ <slab::Slab<T> as core::iter::traits::collect::FromIterator<(usize,T)>>::from_iter::h376b5c161a9769d4
        +682 ┊ <slab::Slab<T> as core::iter::traits::collect::FromIterator<(usize,T)>>::from_iter::h49f7d6b7a1e0c471
        -679 ┊ alloc::collections::btree::fix::<impl alloc::collections::btree::node::NodeRef<alloc::collections::btree::node::marker::Mut,K,V,alloc::collections::btree::node::marker::LeafOrInternal>>::fix_node_through_parent::h8ea3a51f3a27c350
        +679 ┊ alloc::collections::btree::fix::<impl alloc::collections::btree::node::NodeRef<alloc::collections::btree::node::marker::Mut,K,V,alloc::collections::btree::node::marker::LeafOrInternal>>::fix_node_through_parent::hf26bd6dd1bd0bdba
        +668 ┊ alloc::collections::btree::node::BalancingContext<K,V>::bulk_steal_right::h5e84fa32c6c968c9
        -668 ┊ alloc::collections::btree::node::BalancingContext<K,V>::bulk_steal_right::hb6957039477bac16
        -631 ┊ alloc::collections::btree::node::BalancingContext<K,V>::bulk_steal_left::h80360c6cbf16b36b
        +631 ┊ alloc::collections::btree::node::BalancingContext<K,V>::bulk_steal_left::h9a2e883301ee3517
        +552 ┊ alloc::collections::btree::node::BalancingContext<K,V>::do_merge::h4d90002156329b51
        +552 ┊ alloc::collections::btree::node::BalancingContext<K,V>::do_merge::h8e728e34943db055
        -552 ┊ alloc::collections::btree::node::BalancingContext<K,V>::do_merge::hcfa9ee5033320a8b
        -552 ┊ alloc::collections::btree::node::BalancingContext<K,V>::do_merge::hf5a152619aeede29
        -518 ┊ alloc::collections::btree::search::<impl alloc::collections::btree::node::NodeRef<BorrowType,K,V,alloc::collections::btree::node::marker::LeafOrInternal>>::search_tree_for_bifurcation::ha1fa2275d67d2b1a
        +518 ┊ alloc::collections::btree::search::<impl alloc::collections::btree::node::NodeRef<BorrowType,K,V,alloc::collections::btree::node::marker::LeafOrInternal>>::search_tree_for_bifurcation::hb1d6464214f62c02
        +510 ┊ alloc::collections::btree::navigate::<impl alloc::collections::btree::node::NodeRef<BorrowType,K,V,alloc::collections::btree::node::marker::LeafOrInternal>>::find_leaf_edges_spanning_range::h96cc3b78a48daa22
        -510 ┊ alloc::collections::btree::navigate::<impl alloc::collections::btree::node::NodeRef<BorrowType,K,V,alloc::collections::btree::node::marker::LeafOrInternal>>::find_leaf_edges_spanning_range::hc24797ad29f7ec18
        +498 ┊ alloc::collections::btree::node::Handle<alloc::collections::btree::node::NodeRef<alloc::collections::btree::node::marker::Mut,K,V,alloc::collections::btree::node::marker::Leaf>,alloc::collections::btree::node::marker::Edge>::insert_recursing::h12e4ca7cd7896daa
        -492 ┊ alloc::collections::btree::node::Handle<alloc::collections::btree::node::NodeRef<alloc::collections::btree::node::marker::Mut,K,V,alloc::collections::btree::node::marker::Leaf>,alloc::collections::btree::node::marker::Edge>::insert_recursing::h7abbcaf30d032e4e
        -322 ┊ ... and 201 more.
       -1545 ┊ Σ [221 Total Rows]

[melekes]

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