<!-- 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.

for (int i = 0; i <= cs1.m_chain.Height(); ++i) {
        LOCK(::cs_main);
        auto index = cs1.m_chain[i];
        if (i < last_assumed_valid_idx && i >= assumed_valid_start_idx) {
            index->nStatus = BlockStatus::BLOCK_VALID_TREE | BlockStatus::BLOCK_ASSUMED_VALID;
        }
        ++num_indexes;
        if (index->IsAssumedValid()) ++num_assumed_valid;
        
        if (i == (assumed_valid_start_idx - 1)) {
            validated_tip = index;
            BOOST_CHECK(!index->IsAssumedValid());
        }
    }
    BOOST_CHECK_EQUAL(expected_assumed_valid, num_assumed_valid);
    CChainState& cs2 = WITH_LOCK(::cs_main,
        return chainman.InitializeChainstate(&mempool, GetRandHash()));
    reload_all_block_indexes();
    
    
    BOOST_CHECK_EQUAL(cs1.setBlockIndexCandidates.count(validated_tip), 1);
    BOOST_CHECK_EQUAL(cs1.setBlockIndexCandidates.count(assumed_tip), 0);
    BOOST_CHECK_EQUAL(cs1.setBlockIndexCandidates.size(), assumed_valid_start_idx);
    
    BOOST_CHECK_EQUAL(cs2.setBlockIndexCandidates.count(validated_tip), 1);
    BOOST_CHECK_EQUAL(cs2.setBlockIndexCandidates.count(assumed_tip), 1);
    BOOST_CHECK_EQUAL(cs2.setBlockIndexCandidates.size(), num_indexes);
}
BOOST_AUTO_TEST_SUITE_END()