Motivation:

• Every time a knob change, the entire knob panel is rebuild. When you have many knob inside a single use case, this impact performance during your dev journey.
• Every time we swap from 'Knobs' panel to 'Addons' panel, knobs panel is rebuild from scratch which impact again peformance. We can 'keep' alive the panels to avoid this pain.

List of issues which are fixed by the PR

• When enabling Flutter devtools - Show Guidelines screen got greyed #1821 seems to be fixed with this PR.

Screenshots

If applicable, add screenshots to help explain the changes.

Checklist

• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making].
• All existing and new tests are passing.

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