fix(eventstore): precise decimal (#8527)

# 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

Correct behaviour of makefile for load tests.
Rename `latestSequence`-queries to `latestPosition`

internal/v2/eventstore/event_store.go

@@ -2,6 +2,8 @@ package eventstore
 
 import (
 	"context"
+
+	"github.com/shopspring/decimal"
 )
 
 func NewEventstore(querier Querier, pusher Pusher) *EventStore {
@@ -30,12 +32,12 @@ type healthier interface {
 }
 
 type GlobalPosition struct {
-	Position        float64
+	Position        decimal.Decimal
 	InPositionOrder uint32
 }
 
 func (gp GlobalPosition) IsLess(other GlobalPosition) bool {
-	return gp.Position < other.Position || (gp.Position == other.Position && gp.InPositionOrder < other.InPositionOrder)
+	return gp.Position.LessThan(other.Position) || (gp.Position.Equal(other.Position) && gp.InPositionOrder < other.InPositionOrder)
 }
 
 type Reducer interface {