Download button - in preferences for downloading policies

[Akatuoro]

Description

Changes proposed in this pull request:

• Add download button in user preferences for downloading policies
  • Enabled policies and rules are downloaded in datree's Custom Rules format, so that they can either be re-uploaded in busola on another cluster or be used for validation using the datree cli
• Add support for datree's Custom Rules format when loading rule sets
• Fix duplicate enum values in Pod Security Standard rules

Related issue(s)

Enhancement for #2376