test(load): machine jwt profile grant (#8482)

# Which Problems Are Solved

Currently there was no load test present for machine jwt profile grant.
This test is now added

# How the Problems Are Solved

K6 test implemented.

# Additional Context

- part of https://github.com/zitadel/zitadel/issues/8352

.gitignore

@@ -31,6 +31,7 @@ sandbox.go
 google-credentials
 key.json
 .keys/*
+load-test/.keys
 
 # dumps
 .backups