fix(eventstore): use decimal for position (#9881)

# Which Problems Are Solved

Float64 which was used for the event.Position field is [not precise in
go and gets rounded](https://github.com/golang/go/issues/47300). This
can lead to unprecies position tracking of events and therefore
projections especially on cockcoachdb as the position used there is a
big number.

example of a unprecies position:
exact: 1725257931223002628
float64: 1725257931223002624.000000

# How the Problems Are Solved

The float64 was replaced by
[github.com/jackc/pgx-shopspring-decimal](https://github.com/jackc/pgx-shopspring-decimal).

# Additional Changes

Rename `latestSequence`-queries to `latestPosition`

# Additional Context

closes https://github.com/zitadel/zitadel/issues/8863

internal/execution/execution_test.go

@@ -59,7 +59,7 @@ func Test_Call(t *testing.T) {
 			args{
 				ctx:        context.Background(),
 				timeout:    time.Second,
-				sleep:      time.Second,
+				sleep:      2 * time.Second,
 				method:     http.MethodPost,
 				body:       []byte("{\"request\": \"values\"}"),
 				respBody:   []byte("{\"response\": \"values\"}"),