Fix activation fatal when leftover wp_stream_db < 3.0.8 (XWPENG-22)

[shadyvb]

Fixes XWPENG-22.

Base branch: develop

Activating or loading Stream fatals on PHP 8.2+ when a leftover wp_stream_db site option is older than 3.0.8. Install::check() runs inside Plugin::__construct() before $GLOBALS['wp_stream'] (and $plugin->install) exist, so wp_stream_update_auto_308() / _300() called wp_stream_get_instance()->install->install() on null.

This passes the in-construction Install instance from Install::update() into those auto-migration callbacks and uses it for install() when the third argument is a WP_Stream\Install instance. Full 3.0.0 / 3.0.8 schema work still runs (Install::install() / dbDelta).

Commits on this branch

1. Leftover wp_stream_db migration fix — Pass Install into auto-migration callbacks so activation/bootstrap does not call wp_stream_get_instance()->install before the plugin global exists.
2. PHP 8.2 / 8.3 CI — Add PHP 8.2 and 8.3 to CI and local Docker switch-to scripts (default local/Docker PHP remains 7.4).
3. Action Scheduler guards (617e4036) — When an outdated Action Scheduler copy is already in memory, Stream no longer fatals on missing as_has_scheduled_action() / other as_* APIs. AS_Scheduler function_exists()-guards those calls.
4. Two Factor login guard (5fe97c0c) — Guard failed-login logging when the user cannot be resolved (avoids fatals during Two Factor flows).
5. wp_stream_get_instance() null guard (9af8a570) — Guard callers when the plugin global is not set.
6. PHPUnit Install coverage — Tests for empty wp_stream_db during construction (AC 9 clean install) and leftover 3.0.0 (auto_308 path only). Tests for wp_stream_db < 3.0.0 are intentionally skipped so auto_300 cannot RENAME/DROP the PHPUnit schema.

Sub-issue #3 (uninstall) — Skipped in this PR.

Checklist

• Project documentation has been updated to reflect the changes in this pull request, if applicable.
• I have tested the changes in the local development environment (see contributing.md).
• I have added phpunit tests.

Release Changelog

• Fix: Fatal error on activation when a leftover Stream database version older than 3.0.8 is present.
• Fix: Fatal error when an outdated Action Scheduler copy is loaded and as_has_scheduled_action() (or other as_* APIs) are missing.
• Fix: Fatals when Two Factor failed-login logging cannot resolve a user.
• Fix: Fatals when code calls wp_stream_get_instance() before the plugin global is set.

Release checklist (version bumps, readme.txt, GitHub release) applies at release time, not in this PR.

Test plan

• PHPUnit Test_Install (single-site and multisite): leftover wp_stream_db=3.0.7 during construction does not fatal; schema includes user_role.
• PHPUnit Test_Install: empty wp_stream_db during construction installs (AC 9); leftover 3.0.0 uses auto_308 path without fatal.
• Local WP-CLI: deactivate Stream, set site option wp_stream_db to 3.0.7, network-activate stream-src — succeeds, option becomes current plugin version, no new debug.log lines.
• Confirm Network Admin → Plugins shows Stream active (no “triggered a fatal error” notice).
• Confirm Stream → Records loads after leftover-migration bootstrap.
• CI lint and e2e matrix rows for PHP 7.4 (default image tag latest), 8.2, and 8.3 all pass. Default local/Docker PHP remains 7.4.
• PHPUnit Test_AS_Scheduler (single-site and multisite): enqueue / recurring / next_scheduled / unschedule when bundled AS is present.
• Local WP-CLI: stub ActionScheduler class with no as_* functions, then has_scheduled / schedule_recurring / enqueue_async / next_scheduled — no fatal; methods no-op or return false.

Change [ ] to [x] to mark the items as done.