refactor: Move pruning/reindex/importing globals to blockstorage

Summary:
Can be reviewed with --color-moved=dimmed-zebra

This is a backport of core#21727 [1/4]
https://github.com/bitcoin/bitcoin/pull/21727/commits/fa81c30c6f1adac79517c958090db174eb6aeda2

Note:

• see discussion in D4624 for why IsBlockPruned wasn't inlined
• the #include <node/blockstorage.h> in src/interfaces/node.cpp should have been added in D11350

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, sdulfari

Reviewed By: #bitcoin_abc, sdulfari

Differential Revision: https://reviews.bitcoinabc.org/D12032