Rename pre / post fork types

[nflaig]

Somehing we should consider for the 2.0 release is to rename pre / post fork types as current semantics are confusing and require feature awareness of each fork instead of just knowing about the fork name itself, and order of forks, which is simple since it's alphabetical.

e.g.

ForkPreBlobs --> ForkPreDeneb

ForkBlobs --> ForkPostDeneb

isForkBlobs --> isForkPostDeneb

etc.

see https://github.com/ChainSafe/lodestar/blob/unstable/packages/params/src/forkName.ts

[philknows]

Related #7011

[ensi321]

What's the reason we want to wait for 2.0 to make this change? Seems to me is just a straightforward refactor in the code.

Unless this feature is notable enough that we want to promote it as part of 2.0 launch

[nflaig]

What's the reason we want to wait for 2.0 to make this change?

we should avoid breaking changes to @lodestar/types without bumping the major version, in case of this refactor, I don't think it's that urgent