Add promoted operators

[vincenthongzy]

Two pages with slightly different information displayed:

1. /operators
2. /avs/:address/operators

Some edge cases to consider:

1. When we search for operators, we should always display the ads even if the result is empty.
2. In /avs/:address/operators, it is ok to not show promoted operators if they are not currently securing the AVS
3. If the promoted operators endpoint fails, we don't need to display error.

Backend PR:
https://github.com/NethermindEth/restaking-dashboard-backend/pull/114

[Zishan-7]

On /operators page when search result is empty, the promoted operators rows expand to take all of the available space

Also ETH -> USD conversion shows NaN when search result is empty. This happens on the AVS details page as well

[vincenthongzy]

On /operators page when search result is empty, the promoted operators rows expand to take all of the available space

Also ETH -> USD conversion shows NaN when search result is empty. This happens on the AVS details page as well

Hm strange, the expanding rows on empty results should have been fixed already, I'll take a close look thanks!

[vincenthongzy]

On /operators page when search result is empty, the promoted operators rows expand to take all of the available space

Also ETH -> USD conversion shows NaN when search result is empty. This happens on the AVS details page as well

Fixed by decoupling the promoted operators' rate and normal operators' rate on both BE and FE

[rubo]

Why no error handling?

[vincenthongzy]

If the promoted operators endpoint fails, we don't need to display error, so we just swallow it up

[rubo]

That TODO confused me.

[vincenthongzy]

I'll reword this comment