Release v7.0.0-beta.clean

[michaelsproul]

Plan for release v7.0.0-beta.clean:

Merge cleaned up versions of the necessary changes from holesky-rescue into release-v7.0.0. This will make it easier to reconcile the release with unstable in future.

• Add CLI flag for additional block bans, but keep default ban: Add block ban flag --invalid-block-roots #7042
• Specialise default block ban for Holesky: Add block ban flag --invalid-block-roots #7042
• Remove 2 + 2 == 5 hacks: Use sync_tolerance_epochs flag to control the proposer prep routines #7044
• Cherry pick --disable-attesting changes for the VC into a clean PR: Add --disable-attesting flag to validator client #7046
• Add a flag for lengthening the VC timeouts used by --use-long-timeouts (we hardcoded 25x in holesky-rescue): https://github.com/sigp/lighthouse/pull/7041/files#r1971104870. @macladson
• Implement short-term memory optimisations described here: Lighthouse OOM mitigations #7053.
• Merge all changes made for v7.0.0-beta.2: manual finalization, BlocksByRoot/Status fixes, etc

[michaelsproul]

We can PR changes to the (now misleadingly named) disable-attesting branch

[eserilev]

for all the block ban related changes (cli flag, default block ban for holesky)
michaelsproul#8

[eserilev]

remove fork choince endpoint
michaelsproul#9

[paulhauner]

We've changed course and will be releasing v7.0.0-beta.1 as a Holesky hot-fix: #7041

See #7040 for more Holesky recovery info.

[michaelsproul]

I think for the "cleaner" release we can use the same sync-threshold flag to control the proposer prep routines. Rather than a new flag or the current always-true approach

[macladson]

CLI flag to control long timeouts: #7047