Convert MZ_HISTORY_RETENTION_STRATEGIES to a builtin mv

[SangJunBak]

• Converts MZ_HISTORY_RETENTION_STRATEGIES to a builtin materialized view. Read commit messages for more details

Motivation

Closes SQL-701

Verification

• Created a new SLT to test the SQL itself.
• Diffed this relation using a customer's workload replay against main and this branch.

[linear-code]

SQL-701

SQL-703

[ggevay]

LGTM, just minor comments

[ggevay]

This only sees durable overrides (ALTER SYSTEM, LaunchDarkly and the config-file sync). A metrics_retention passed as --system-parameter-default never reaches mz_overridden_system_parameters: with metrics_retention=1h as a process default, SHOW metrics_retention says 1 h and the old table reported 3600000 for mz_cluster_replica_sizes, while this reports 2592000000. The underlying gap is that no relation shows effective parameter values (SQL-757), so a sentence here saying that is enough for this PR. Also worth a line in the description: these rows now follow ALTER SYSTEM SET metrics_retention immediately, where the old table kept the boot-time value until the next restart.

[ggevay]

Nothing here creates a subsource or progress relation, so the view's 'subsource' type filter is unguarded: dropping it loses 6 of the 7 rows below and this file still passes. Appended at the end of this file, this passes on the PR's CI image (and fails when an expected value is changed); the values match the old table:

statement ok
CREATE SOURCE lg_auction IN CLUSTER quickstart FROM LOAD GENERATOR AUCTION FOR ALL TABLES WITH (RETAIN HISTORY FOR '6m')

query TT
SELECT o.name, h.value
FROM mz_internal.mz_history_retention_strategies h
JOIN mz_catalog.mz_objects o ON o.id = h.id
WHERE o.name IN ('lg_auction', 'lg_auction_progress', 'accounts', 'auctions', 'bids', 'organizations', 'users')
ORDER BY o.name
----
accounts  360000
auctions  360000
bids  360000
lg_auction  360000
lg_auction_progress  360000
organizations  360000
users  360000