increase max label length for firewall and rule resources

[bregmanx]

📝 Description

What does this PR do and why is this change necessary?
This PR updates the schema validators for linode_firewall and linode_firewall_rule resources.
Previously, labels were restricted to a maximum of 32 characters. In environments where descriptive, programmatically generated labels are used, this limit can be too restrictive.
By raising the limit to 64 characters, users gain more flexibility in naming their firewall resources.

✔️ How to Test

Unit Testing

make test-unit

Integration Testing

Run the relevant firewall integration tests:

make test-int PKG_NAME=firewall
make test-int PKG_NAME=firewalls
make test-int PKG_NAME=firewallrule
make test-int PKG_NAME=firewallrules

Manual Testing

In a terraform-provider-linode sandbox environment (e.g. dx-devenv), apply the following configuration:

resource "linode_firewall" "test" {
  label = "tf-test-firewall-label-with-more-than-thirty-two-chars"
  inbound {
    action   = "ACCEPT"
    protocol = "TCP"
    ports    = "22"
    ipv4     = ["0.0.0.0/0"]
  }
  outbound {
    action   = "ACCEPT"
    protocol = "ALL"
    ipv4     = ["0.0.0.0/0"]
  }
}

resource "linode_firewall_rule" "test" {
  label       = "tf-test-firewall-rule-label-longer-than-thirty-two-chars"
  firewall_id = linode_firewall.test.id
  action      = "ACCEPT"
  protocol    = "TCP"
  ports       = "80"
  ipv4        = ["0.0.0.0/0"]
  description = "test rule with long label"
}

Steps:

1. Run terraform apply and verify the provider accepts labels up to 64 characters.
2. Run terraform plan again and ensure no changes are proposed.
3. Adjust the labels above 64 characters and confirm the provider rejects them.