fix(packaging): update rulesStorageDirectory to /var/lib/loki/rules in operator (#7748)

[ankitshokeen]

Fixes #7748. Updated rulesStorageDirectory to /var/lib/loki/rules in operator/internal/manifests/var.go for persistent storage, aligning with production Helm configs. Verified local configs use /var/lib/loki. Tested with:

• make loki and local run with loki-local-config.yaml.
• Operator deployment via Kind, confirming /var/lib/loki/rules mount.
• make test for unit tests.
  Note: /var/lib/loki may require permissions (e.g., sudo chown).

[CLAassistant]

All committers have signed the CLA.

[xperimental]

I will probably take a look at this next week. Currently I'm a bit confused on what it tries to do, the linked issue seems to indicate a bit of a misunderstanding, but we'll get to the bottom of this.

General note: If the PR should fix something that is related to the operator then the changes should be limited to the operator/ directory.