fix(transaction): fix previous snapshot summary fetching

[dentiny]

Which issue does this PR close?

• Closes BUG: snapshot summary doesn't consider previous summary #2390

What changes are included in this PR?

The root cause for the issue is, we use the current snapshot id (which hasn't been reflected to table metadata yet) to get previous snapshot summary.

Are these changes tested?

Yes.

[dentiny]

The failure doesn't seem to be related to my change.

[timactive]

+1

fix, `total-records` of the new snapshot was set to `added-records`
(=2 for a 2-row delta) instead of `parent.total + added` (=484065).
With the patch applied locally, the snapshot summary correctly
reports the cumulative and downstream consumers reading metadata.json
directly (iceberg-java in our case) see the right value on the next
commit. 36/36 snapshot tests stay green.

Edge case for the docs / future follow-up: tables with history
already corrupted by the buggy version will keep propagating wrong
totals because parent.total-records is read as-is. In practice
re-bootstrapping unblocks; a chain-walk recompute could self-heal
if needed, but it's not warranted for this PR. Thanks for the fix!```

[dentiny]

Hi @Xuanwo I'm wondering if you could take a look when you have some time? Thank you!

[CTTY]

LGTM! just one comment

[CTTY]

LGTM! Thanks for the fix!