1843 - limit cache when close to tip

[Cmdv]

Description

This fixes #1843

Checklist

• Commit sequence broadly makes sense
• Commits have useful messages
• New tests are added if needed and existing tests are updated
• Any changes are noted in the changelog
• Code is formatted with fourmolu on version 0.10.1.0 (which can be run with scripts/fourmolize.sh)
• Self-reviewed the diff

Migrations

• The pr causes a breaking change of type a,b or c
• If there is a breaking change, the pr includes a database migration and/or a fix process for old values, so that upgrade is possible
• Resyncing and running the migrations provided will result in the same database semantically

If there is a breaking change, especially a big one, please add a justification here. Please elaborate
more what the migration achieves, what it cannot achieve or why a migration is not possible.

[kderme]

optimiseCaches requires fixing.
Also optomise is sometimes used instead of optimise. Using reduce instead of optimise would also make it more specific, since the cache is reduced.
Finally, using patterns as suggested could reduce the cases.

[kderme]

possibly the new boolean flag need to become a TVar

[kderme]

Just a few stylistic changes and this is good to go