Zoekt: Add reallocation scheduling task

What does this MR do and why?

This MR takes the script from the recent incident and turns it into a scheduling task

Database plans

Search::Zoekt::EnabledNamespace.where(id: node.indices.where(namespace_id: namespace_ids).select(:zoekt_enabled_namespace_id)).update_all(search: false, updated_at: Time.zone.now)

UPDATE "zoekt_enabled_namespaces" SET "search" = FALSE, "updated_at" = '2024-04-03 15:23:22.695030' WHERE "zoekt_enabled_namespaces"."id" IN (SELECT "zoekt_indices"."zoekt_enabled_namespace_id" FROM "zoekt_indices" WHERE "zoekt_indices"."zoekt_node_id" = 10 AND "zoekt_indices"."namespace_id" IN (72020569, 81929366, 7811657, 67858724, 14160629, 71707741, 62051980, 72193585, 9526127, 57349364, 71607218, 70922445, 81433216, 11626435, 15880505, 12443608, 61051508, 6730621, 68890757, 53786701, 71137932, 81412065, 9630740, 8474779, 73919614, 14147582, 81340449, 75649675, 9619442, 65699212, 65641627, 78989449, 71684218, 55310482, 70922438, 1298254, 12962032, 70106642, 70682852, 79389339, 69991962, 80029847, 61737019, 4642167, 65818294, 6686912, 918966, 59466828, 69476815, 81794881, 11370458, 10316576, 72278023, 80428365, 7240525, 7850346, 13164390, 64635561, 8533346, 12208853, 6545253, 356589, 70204826, 81804984, 80473287, 81815306, 79739972, 4339527, 13482440, 4975871, 8659214, 52528073, 77292406, 70633179, 70460392, 5394771, 1633852, 5851859, 79600636, 53288043, 11375272, 13563809, 77382551, 6098577, 65476155, 68047298, 54502395, 65866462, 7509264, 62099140, 2299361, 67126387, 70682062, 59137690, 15081863, 73887932, 68582018, 64580754, 16012241, 78649991))

https://postgres.ai/console/gitlab/gitlab-production-main/sessions/27355/commands/85132

node.indices.where(namespace_id: namespace_ids).destroy_all

This query performs individual destroy calls for the batch of up to 100 indices

SELECT "zoekt_indices".* FROM "zoekt_indices" WHERE "zoekt_indices"."zoekt_node_id" = 10 AND "zoekt_indices"."namespace_id" IN (72020569, 81929366, 7811657, 67858724, 14160629, 71707741, 62051980, 72193585, 9526127, 57349364, 71607218, 70922445, 81433216, 11626435, 15880505, 12443608, 61051508, 6730621, 68890757, 53786701, 71137932, 81412065, 9630740, 8474779, 73919614, 14147582, 81340449, 75649675, 9619442, 65699212, 65641627, 78989449, 71684218, 55310482, 70922438, 1298254, 12962032, 70106642, 70682852, 79389339, 69991962, 80029847, 61737019, 4642167, 65818294, 6686912, 918966, 59466828, 69476815, 81794881, 11370458, 10316576, 72278023, 80428365, 7240525, 7850346, 13164390, 64635561, 8533346, 12208853, 6545253, 356589, 70204826, 81804984, 80473287, 81815306, 79739972, 4339527, 13482440, 4975871, 8659214, 52528073, 77292406, 70633179, 70460392, 5394771, 1633852, 5851859, 79600636, 53288043, 11375272, 13563809, 77382551, 6098577, 65476155, 68047298, 54502395, 65866462, 7509264, 62099140, 2299361, 67126387, 70682062, 59137690, 15081863, 73887932, 68582018, 64580754, 16012241, 78649991)

https://postgres.ai/console/gitlab/gitlab-production-main/sessions/27355/commands/85133

Batching over indices

SELECT "zoekt_indices"."namespace_id" FROM "zoekt_indices" WHERE "zoekt_indices"."zoekt_node_id" = 10 AND "zoekt_indices"."id" >= 13633 AND "zoekt_indices"."id" < 17485

Before adding a composite index: https://postgres.ai/console/gitlab/gitlab-production-main/sessions/27383/commands/85249

After adding a composite index: https://postgres.ai/console/gitlab/gitlab-production-main/sessions/27383/commands/85252

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Before	After

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#454289 (closed)