chore(Dashboard): Remove unnecessary loading

[geido]

SUMMARY

The goal of this PR is unblock the Dashboard skeleton (showing of the filters, tabs, charts containers, etc.) progressively so that the user experience is improved by showing available content sooner rather than later.

The work on this PR was becoming too large, leading to the decision of splitting the changes in smaller chunks. The thread will be updated with all related PRs.

TESTING INSTRUCTIONS

1. The Dashboard should load normally.
2. A Dashboard with a pre-selected filter value should load successfully.

ADDITIONAL INFORMATION

• [ ] Has associated issue:
• [ ] Required feature flags:
• [ ] Changes UI
• [ ] Includes DB Migration (follow approval process in SIP-59)
  • [ ] Migration is atomic, supports rollback & is backwards-compatible
  • [ ] Confirm DB migration upgrade and downgrade tested
  • [ ] Runtime estimates and downtime expectations provided
• [ ] Introduces new feature or API
• [ ] Removes existing feature or API

[geido]

This PR will be superseded by smaller PRs. I will update this thread accordingly:

https://github.com/apache/superset/pull/30440 https://github.com/apache/superset/pull/30611