Fix vlan id should be integer type (backport #1099)

[mergify]

Summary

• fix vlan id should be integer type
• allow user to modify vlan Id with empty value
• ensure input value should between 1 ~ 4094

PR Checklist

• Is this a multi-tenancy feature/bug?
  • Yes, the relevant RBAC changes are at:
• Do we need to backport changes to the old Rancher UI, such as RKE1?
  • Yes, the relevant PR is at:
• Are backend engineers aware of UI changes?
  • Yes, the backend owner is:

Related Issue #

• [backport v1.3] [BUG] VM Network's vlan property now in UI as string, validator expects int  harvester#6311
• [BUG] [UI] Create VM Network VLAN ID input validation buggy harvester#6290

Occurred changes and/or fixed issues

Technical notes summary

Note. this PR should backport to v1.4 / v1.3 / v1.2

Areas which could experience regressions

Screenshot/Video

fixed.mov

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This is an automatic backport of pull request #1099 done by [Mergify](https://mergify.com).