Register custom xlog reader callbacks for on-demand WAL download in StartupDecodingContext (#9007)

## Problem

See https://github.com/neondatabase/neon/issues/8931
On-demand WAL download are not set in all cases where WAL is accessed by
logical replication

## Summary of changes

Set customer xlog reader handles in StartupDecodingContext

Related changes in Postgres modules:

https://github.com/neondatabase/postgres/pull/495
https://github.com/neondatabase/postgres/pull/496
https://github.com/neondatabase/postgres/pull/497
https://github.com/neondatabase/postgres/pull/498

## Checklist before requesting a review

- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.

## Checklist before merging

- [ ] Do not forget to reformat commit message to not include the above
checklist

---------

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>

vendor/revisions.json

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