do not swallow panic when rolling back inner panic to prevent connection leak

[sio4]

This PR makes Transaction() not swallow inner panic when rolling back inner panic to prevent connection leak. (followup for #748, #775)

fixes #793

With this configuration,

app.GET("/panic", func(c buffalo.Context) error {
        panic("panic message")
})

Previously we got a generic error but no information about the actual panic:

[POP] 2022/11/19 12:27:13 sql - BEGIN Transaction --- (conn=tx-2490861061155653040, tx=2490861061155653040)
[POP] 2022/11/19 12:27:13 sql - ROLLBACK Transaction (inner function panic) --- (conn=tx-2490861061155653040, tx=2490861061155653040)
ERRO[2022-11-19T12:27:13+09:00] transaction was rolled back due to inner panic conn=tx-2490861061155653040 db=0s params="{}" request_id=f3afa8520e74468e3126-605aa30f89aa98d921a6 status=500 tx=2490861061155653040
INFO[2022-11-19T12:27:13+09:00] /panic/ conn=tx-2490861061155653040 db=0s duration=4.668962ms human_size="33 kB" method=GET params="{}" path=/panic/ request_id=f3afa8520e74468e3126-605aa30f89aa98d921a6 size=33278 status=500 tx=2490861061155653040

now, the panic message will be handled by Buffalo's panic handler (or the application using Pop just gets the panic)

[POP] 2022/11/19 12:29:19 sql - BEGIN Transaction --- (conn=tx-6882700540045613063, tx=6882700540045613063)
[POP] 2022/11/19 12:29:19 sql - ROLLBACK Transaction (inner function panic) --- (conn=tx-6882700540045613063, tx=6882700540045613063)
ERRO[2022-11-19T12:29:19+09:00] panic message conn=tx-6882700540045613063 db=0s params="{}" request_id=d03cd4eaaeb706091e72-bd2ebc6009256e976b7e status=500 tx=6882700540045613063
INFO[2022-11-19T12:29:19+09:00] /panic/ conn=tx-6882700540045613063 db=0s duration=4.387724ms human_size="33 kB" method=GET params="{}" path=/panic/ request_id=d03cd4eaaeb706091e72-bd2ebc6009256e976b7e size=33245 status=500 tx=6882700540045613063

Developers can use https://github.com/gobuffalo/events/ for more details:

func init() {
    events.Listen(func(e events.Event) {
        switch e.Kind {
        case events.ErrPanic:
            fmt.Println("panic error:", e.Error)
            if pl, ok := e.Payload["data"].(map[string]interface{}); ok {
                fmt.Println("panic stacktrace:", pl["stacktrace"])
            }
        }
    }) 
}

(Payload has a bug having additional "data", and will be fixed soon)

The above code will print the following:

panic error: panic message
panic stacktrace: goroutine 66 [running]:
runtime/debug.Stack()
        /opt/google/go/src/runtime/debug/stack.go:24 +0x65
github.com/gobuffalo/buffalo.(*App).PanicHandler.func1.1()
        /home/sio4/go/github.com/gobuffalo/buffalo/errors.go:98 +0x1e5
panic({0xbc8760, 0x1345270})
        /opt/google/go/src/runtime/panic.go:1038 +0x215
github.com/gobuffalo/pop/v6.(*Connection).Transaction.func1.1()
        /home/sio4/go/github.com/gobuffalo/pop/connection.go:173 +0xc5
panic({0xbc8760, 0x1345270})
        /opt/google/go/src/runtime/panic.go:1038 +0x215
coco/actions.App.func1.6({0xc000228001, 0xc000322f60})
        /home/sio4/git/bt/coco/actions/app.go:94 +0x27