Fleet UI: Set default pagination length to 20

[RachelElysia]

Cerra #7144

FIX

• Update default pagination page size from 100 to 20 and enable pagination for Queries, Schedule, and Policies table

Other tech debt address

• Remove unnecessary plumbing of "policies" text for resultsTitle and !!queriesList for searchable (set on TableContainer component doesn't need it passed through parent component)
• Change isFetchingGlobalScheduledQueries to isLoadingGlobalScheduledQueries because global scheduled queries is not refetched

Checklist for submitter

If some of the following don't apply, delete the relevant line.

• [x] Changes file added for user-visible changes (in changes/ and/or orbit/changes/).
• [x] Manual QA for all new/changed functionality