chore: avoid remsh node name overflow atom table

[lafirest]

The remsh node name is generated to be unique, this may cause atom leakage, so we need to change the generation rule to limit the total of these names

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Changed lines covered in coverage report
• Change log has been added to changes/ dir
• For EMQX 4.x: appup files updated (execute scripts/update-appup.sh emqx)
• For internal contributor: there is a jira ticket to track this change
  EMQX-8221
• If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
• In case of non-backward compatible changes, reviewer should check this item as a write-off, and add details in Backward Compatibility section

Backward Compatibility

More information

[zmstone]

Just to be clear, this is NOT any attack.
If an attacker gained access to run emqx shell commands, atom table overflow is perhaps the least to care about.