Add reload command to pick up externally modified analysis files

[jozanek]

Bloop reads each project's persisted compilation state once and keeps it in memory, so state replaced on disk — restoring a cache saved from an earlier run, say — is invisible until a restart.

Adds a way to re-read it:

• CLI: bloop reload, all projects or --project
• BSP: bloop/reloadAnalysis, given targets or all

A reload replaces every requested project or nothing. It fails, untouched, while a project compiles or is cleaned, if state changes mid-read, or if what's on disk can't be used; BSP errors carry a stable reason and retryable flag. Persisted state is only adopted when the output directory it names is one Bloop manages for that project — compilation later deletes that directory, so an unvalidated path would eventually be removed recursively.

workspace/reload is implemented as configuration-only (Bloop already reloads config per request) and never imports state, so it can't fail for unrelated reasons.

Closes #1091. The remaining half of that discussion — sharing state across machines or checkouts — is blocked by absolute paths in the persisted state and is tracked in #1351.

Known issue: after a reload, an earlier-started request can leave a stale latest result, affecting BSP diagnostic carry-over only — the successful result compilation builds on is authoritative.

Tests: ReloadAnalysisSpec (12) and BspReloadSpec (3 per transport).