API v2: Add sorting to tokens page

[sl1depengwyn]

Part of #7794

Changelog

Added two new query parameters for api/v2/tokens endpoint

• sort - possible values: fiat_value, holder_count, circulating_market_cap
• order - possible values: asc, desc

Added fiat_value to next_page_params to be able to sort by fiat_value, note that it should not break the new UI

This PR can be tested in the old ui on the https://github.com/blockscout/blockscout/tree/mf-add-tokens-sorting-test branch by adding these new query parameters by hand

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools