fix: flowise-186 (#6158)

* update: type field for some credentials where string type could expose secrets

* update: contribution docs with note on adding credential files

* update: add reveal for url type, permissions for get credential by id

* fix: review feedback

* fix: review feedback

* update: agentflow package with credentials ui changes

* fix: test coverage, add tests for changes in CreateCredentialDialog

* revert: changes to agentflows package