Opening two of the same wallet (tested in v0.18.0 of bitcoin-qt 64 bit) will cause a database collision, and will crash the program.

`[marshall@likon] {21:21} [~] $ bitcoin-0.18.0/bin/bitcoin-qt `
`terminate called after throwing an instance of 'std::runtime_error'  what():  BerkeleyBatch: Can't open database 8204388-wallet.dat (duplicates fileid 8b1c090000000800e25686350000000000000000 from 1352491-wallet.dat)`
`Aborted (core dumped)`

I have been able to reproduce the issue by importing two of the same wallet (with different filenames).
#include <util/moneystr.h>
#include <util/rbf.h>
#include <util/translation.h>
#include <wallet/coincontrol.h>
#include <wallet/fees.h>
#include <algorithm>
#include <assert.h>
#include <boost/algorithm/string/replace.hpp>
const std::map<uint64_t,std::string> WALLET_FLAG_CAVEATS{
    {WALLET_FLAG_AVOID_REUSE,
        "You need to rescan the blockchain in order to correctly mark used "
        "destinations in the past. Until this is done, some destinations may "
        "be considered unused, even if the opposite is the case."
    },
};
static const size_t OUTPUT_GROUP_MAX_ENTRIES = 10;
static RecursiveMutex cs_wallets;
static std::vector<std::shared_ptr<CWallet>> vpwallets GUARDED_BY(cs_wallets);
static std::list<LoadWalletFn> g_load_wallet_fns GUARDED_BY(cs_wallets);
bool AddWallet(const std::shared_ptr<CWallet>& wallet)
{
    LOCK(cs_wallets);
    assert(wallet);
    std::vector<std::shared_ptr<CWallet>>::const_iterator i = std::find(vpwallets.begin(), vpwallets.end(), wallet);
    if (i != vpwallets.end()) return false;
    vpwallets.push_back(wallet);
    wallet->ConnectScriptPubKeyManNotifiers();
    return true;
}
bool RemoveWallet(const std::shared_ptr<CWallet>& wallet)