fix(all): critical fixes to the libevm branch

[qdm12]

Why this should be merged

Critical fixes only from review on #1501

Minor changes can be applied in #1552

How this works

How this was tested

Need to be documented?

Need to update RELEASES.md?

[ARR4N]

If these are critical then they need tests, specifically ones that:

1. Confirm that the ETH upgrades have been applied; and
2. Verify a ChainConfig with invalid FeeConfig.

[qdm12]

Tests added:

• ChainConfig Description() test TestChainConfigDescription
• ChainConfig Verify test TestChainConfigVerify (Verify coverage, does not test in-depth unlike other existing tests such as precompile ones)
• Genesis params.SetEthUpgrades test stolen from coreth TestGenesisEthUpgrades and adapted with small changes, with the aim of having small diffs between the 2 repositories.

[ARR4N]

Approving with the caveat of the comments I've made. This will still need Cey's review as a code owner.