feat: adapt pg-aggregates for Constructive conventions

Adapt the imported @graphile/pg-aggregates v5 sources for Constructive's
codebase conventions and custom connection-filter fork.

Changes from upstream:
- Build system: yarn/tsc → pnpm/makage with CJS+ESM outputs
- Remove upstream config files (.yarn, .yarnrc.yml, .eslintignore,
  .prettierrc.js, .jest-babel-transform.js, jest.config.js, etc.)
- Remove upstream test files (depend on yarn/jest infrastructure)
- Imports: Replace subpath exports (postgraphile/grafast,
  graphile-build-pg/@dataplan/pg) with direct package imports
  for moduleResolution: node compatibility
- FilterRelationalAggregatesPlugin: Read from $where._manyRelation
  (our ConnectionFilterBackwardRelationsPlugin) instead of upstream's
  $where.extensions.pgFilterRelation
- Plugin ordering: before ConnectionFilterArgPlugin (our fork's name)
- Field naming: Aggregate sub-filter field renamed from 'filter' to 'where'
- Version: Inline const version instead of require('../package.json')
- Remove .js extensions from local imports
- Add PgConditionExtensions augmentation for pgFilterAttribute
- Add graphile-connection-filter and grafast as peer dependencies
- Wire PgAggregatesPreset into ConstructivePreset in graphile-settings
- Update schema snapshots in graphql/test and graphql/server-test

Provides: aggregates field on connections (sum, avg, min, max, stddev,
variance, distinctCount), groupedAggregates with groupBy + having,
orderBy relational aggregates, filter by relational aggregates.
Per-table opt-out via @behavior -aggregates smart tag.

Author: pyramation