<!-- Describe the issue -->

When our chainstate activation sequence fails and we're running the GUI, we ask the user via a question box whether or not they'd like to re-run the sequence with `fReindex = true`. Fun fact: despite the fact that this sequence is wrapped in a while loop, we only run it twice at most.

https://github.com/bitcoin/bitcoin/blob/7ecb309c4ed1bb9ae6b9a12cbb4f083328edc125/src/init.cpp#L1539-L1556

If they answer yes, the sequence will always fail, because a chainstate will have already been initialized in the original run and `InitializeChainstate` will throw a `std::logic_error`:

https://github.com/bitcoin/bitcoin/blob/7ecb309c4ed1bb9ae6b9a12cbb4f083328edc125/src/validation.cpp#L4573-L4594

This always reproduces. To reproduce:
```
gdb ./src/qt/bitcoin-qt
(gdb) b InitializeChainstate
(gdb) # add breakpoint for the "if (!fLoaded && !ShutdownRequested()) {" line
(gdb) r  # should stop at the breakpoint for InitializeChainstate
(gdb) c  # to advance to the breakpoint for the "if (!fLoaded && !ShutdownRequested()) {" line
(gdb) set fLoaded=false
(gdb) c  # should stop at the breakpoint for InitializeChainstate
(gdb) n  # step through InitializeChainstate to see that it throws
```

We expect the re-run of the chainstate activation sequence to not always fail.

{
    ChainstateManager& chainman = *Assert(m_node.chainman);
    CTxMemPool& mempool = *m_node.mempool;
    CChainState& cs1 = chainman.ActiveChainstate();
    int num_indexes{0};
    int num_assumed_valid{0};
    const int expected_assumed_valid{20};
    const int last_assumed_valid_idx{40};
    const int assumed_valid_start_idx = last_assumed_valid_idx - expected_assumed_valid;
    CBlockIndex* validated_tip{nullptr};
    CBlockIndex* assumed_tip{chainman.ActiveChain().Tip()};
    auto reload_all_block_indexes = [&]() {
        for (CChainState* cs : chainman.GetAll()) {
            LOCK(::cs_main);
            cs->UnloadBlockIndex();
            BOOST_CHECK(cs->setBlockIndexCandidates.empty());
        }
        WITH_LOCK(::cs_main, chainman.LoadBlockIndex());
    };
    
    
    reload_all_block_indexes();
    BOOST_CHECK_EQUAL(cs1.setBlockIndexCandidates.size(), cs1.m_chain.Height() + 1);