lint: enable intrange linter (#7331)

Enable intrange linter to enforce modern Go range syntax over
traditional for loops, by converting:

for i := 0; i < n; i++

to:

for i := range n

Adding type conversions where needed for compatibility
with existing uint64 parameters.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

.golangci.yml

@@ -6,6 +6,7 @@ linters:
     - copyloopvar
     - govet
     - ineffassign
+    - intrange
     - staticcheck
     - unconvert
     - unused