Narrow the Query Store slicer's clock-skew margin to an hour; the interval-table move is blocked (#3953)

[erikdarlingdata]

Part of #3953.

Why

#3953 asks the Query Store reads to stop deduplicating the raw slice on every pass. This PR ships one small part of that. The main change needs a design decision first (see "Not in this PR"), so #3953 stays open.

What changes

• ViewerDataService.QueryStoreSlicerSql: the lower chunk-exclusion bound collection_time >= $2 - interval '1 day' becomes collection_time >= $2 - interval '1 hour'.
• The slicer filters its window on COALESCE(interval_start_time_utc, collection_time) >= $2. An interval is always collected after it starts, so a row in the window also has collection_time >= $2. The margin below $2 is there only for clock skew between the monitored server and the store, and an hour covers that. A 24-hour window that ends now reads 25 hours of collection_time instead of 48.
• The upper bound, collection_time <= $3 + interval '30 days', does not change. It covers Query Store's longest interval (1 day) plus up to 29 days of collector outage.
• ViewerQueriesTests.QueryStoreSlicerSql_KeepsSlackenedCollectionTimeBoundsForChunkExclusion pins the new bound, and the comment in the SQL explains it.

Not in this PR

The main change in #3953 moves three Query Store reads onto query_store_interval_latest, the table #4208 added for PLAN_REGRESSION. The table as built cannot serve them:

1. It stores only rows with execution_type_desc = 'Regular', and its key does not include execution_type_desc. All three reads also need the Aborted and Exception rows.
2. Each of the three reads needs columns that the table does not have.

The analysis and the options for a fix are on #3953 (issuecomment-5835309188). #4310 tracks the other Query Store reads that still deduplicate the raw slice.

Test plan

• ViewerQueriesTests.QueryStoreSlicerSql_KeepsSlackenedCollectionTimeBoundsForChunkExclusion checks the new bound.
• No live comparison of the old and new slicer SQL, no EXPLAIN run and no local full suite ran for this PR. CI runs the full suite.
• GitHub Actions CI on ec9690f4: build, Darling PostgreSQL tests and Lite tests all pass.

CHANGELOG entry

SECTION: Fixed
ENTRY:

• The Query Store activity slicer reads less history on each refresh ([Narrow the Query Store slicer's clock-skew margin to an hour; the interval-table move is blocked (#3953) #4311]) - The slicer read one extra day of Query Store history below its window, as a margin for clock skew. The margin is now one hour. For the last 24 hours, it now reads 25 hours of history instead of 48.
  REF:
  [Narrow the Query Store slicer's clock-skew margin to an hour; the interval-table move is blocked (#3953) #4311]: Narrow the Query Store slicer's clock-skew margin to an hour; the interval-table move is blocked (#3953) #4311

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