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/eventstore/handler/v2/state_test.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/shopspring/decimal"
 
 	"github.com/zitadel/zitadel/internal/api/authz"
 	"github.com/zitadel/zitadel/internal/database/mock"
@@ -166,7 +167,7 @@ func TestHandler_updateLastUpdated(t *testing.T) {
 				updatedState: &state{
 					instanceID:     "instance",
 					eventTimestamp: time.Now(),
-					position:       42,
+					position:       decimal.NewFromInt(42),
 				},
 			},
 			isErr: func(t *testing.T, err error) {
@@ -192,7 +193,7 @@ func TestHandler_updateLastUpdated(t *testing.T) {
 				updatedState: &state{
 					instanceID:     "instance",
 					eventTimestamp: time.Now(),
-					position:       42,
+					position:       decimal.NewFromInt(42),
 				},
 			},
 			isErr: func(t *testing.T, err error) {
@@ -217,7 +218,7 @@ func TestHandler_updateLastUpdated(t *testing.T) {
 							eventstore.AggregateType("aggregate type"),
 							uint64(42),
 							mock.AnyType[time.Time]{},
-							float64(42),
+							decimal.NewFromInt(42),
 							uint32(0),
 						),
 						mock.WithExecRowsAffected(1),
@@ -228,7 +229,7 @@ func TestHandler_updateLastUpdated(t *testing.T) {
 				updatedState: &state{
 					instanceID:     "instance",
 					eventTimestamp: time.Now(),
-					position:       42,
+					position:       decimal.NewFromInt(42),
 					aggregateType:  "aggregate type",
 					aggregateID:    "aggregate id",
 					sequence:       42,
@@ -397,7 +398,7 @@ func TestHandler_currentState(t *testing.T) {
 									"aggregate type",
 									int64(42),
 									testTime,
-									float64(42),
+									decimal.NewFromInt(42).String(),
 									uint16(10),
 								},
 							},
@@ -412,7 +413,7 @@ func TestHandler_currentState(t *testing.T) {
 				currentState: &state{
 					instanceID:     "instance",
 					eventTimestamp: testTime,
-					position:       42,
+					position:       decimal.NewFromInt(42),
 					aggregateType:  "aggregate type",
 					aggregateID:    "aggregate id",
 					sequence:       42,