Umbrella issue for 26.0 testing. Please help testing on a wide variety of supported platforms, as well as interaction with different software.

Let us know which version you tested on which operating system.

If you find an issue, please search Github for known issues first and then open a new Github issue.

*This meta issue should not be used to report bugs, as a single thread makes it impossible to track more than one topic.*

See [26.0 Draft Release Notes](https://github.com/bitcoin-core/bitcoin-devwiki/wiki/26.0-Release-Notes-Draft) for a list of changes.

See here for the testing guide: https://github.com/bitcoin-core/bitcoin-devwiki/wiki/26.0-Release-Candidate-Testing-Guide.
*   This chunk is used to carve out blocks.
 *
 * * Block sizes or alignments that can not be served by the pools are allocated
 *   and deallocated by operator new().
 *
 * PoolResource is not thread-safe. It is intended to be used by PoolAllocator.
 *
 * @tparam MAX_BLOCK_SIZE_BYTES Maximum size to allocate with the pool. If larger
 *         sizes are requested, allocation falls back to new().
 *
 * @tparam ALIGN_BYTES Required alignment for the allocations.
 *
 * An example: If you create a PoolResource<128, 8>(262144) and perform a bunch of
 * allocations and deallocate 2 blocks with size 8 bytes, and 3 blocks with size 16,
 * the members will look like this:
 *
 *     m_free_lists                         m_allocated_chunks
 *        ┌───┐                                ┌───┐  ┌────────────-------──────┐
 *        │   │  blocks                        │   ├─►│    262144 B             │
 *        │   │  ┌─────┐  ┌─────┐              └─┬─┘  └────────────-------──────┘
 *        │ 1 ├─►│ 8 B ├─►│ 8 B │                │
 *        │   │  └─────┘  └─────┘                :
 *        │   │                                  │
 *        │   │  ┌─────┐  ┌─────┐  ┌─────┐       ▼
 *        │ 2 ├─►│16 B ├─►│16 B ├─►│16 B │     ┌───┐  ┌─────────────────────────┐
 *        │   │  └─────┘  └─────┘  └─────┘     │   ├─►│          ▲              │ ▲
 *        │   │                                └───┘  └──────────┬──────────────┘ │
 *        │ . │                                                  │    m_available_memory_end
 *        │ . │                                         m_available_memory_it
 *        │ . │