feat(debug): small improvements to validator debug page

[Trisfald]

Following up on the ideas shared by @Longarithm, I removed the shards column and merged the shards information into the role of CP (chunk producer), recovering some space in the page.

Also fix to display the role CP in the next epoch.

[Trisfald]

Preview

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 71.65%. Comparing base (fc3c82c) to head (dd1d7ae).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #11674 +/- ## ========================================== - Coverage 71.66% 71.65% -0.01% ========================================== Files 788 788 Lines 161374 161374 Branches 161374 161374 ========================================== - Hits 115645 115639 -6 - Misses 40691 40702 +11 + Partials 5038 5033 -5 ``` | [Flag](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | Coverage Δ | | |---|---|---| | [backward-compatibility](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `0.23% <ø> (ø)` | | | [db-migration](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `0.23% <ø> (ø)` | | | [genesis-check](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `1.36% <ø> (ø)` | | | [integration-tests](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `37.87% <ø> (+0.02%)` | :arrow_up: | | [linux](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `69.06% <ø> (+<0.01%)` | :arrow_up: | | [linux-nightly](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `71.16% <ø> (-0.01%)` | :arrow_down: | | [macos](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `51.07% <ø> (-1.57%)` | :arrow_down: | | [pytests](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `1.59% <ø> (ø)` | | | [sanity-checks](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `1.39% <ø> (ø)` | | | [unittests](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `66.23% <ø> (-0.03%)` | :arrow_down: | | [upgradability](https://app.codecov.io/gh/near/nearcore/pull/11674/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near) | `0.28% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=near#carryforward-flags-in-the-pull-request-comment) to find out more.

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