[lacros] Refine BrowserManager update handling

This CL adds a browser version delegate to keep track of the version
number of the most recently loaded lacros-chrome binary from the
BrowserLoader.

The browser version delegate in BrowserManager is now the single source of truth as to what the latest launchable version is and whether an update should be attempted.

This simplifies the current state of the world in a few ways

  - The browser version delegate now encapsulates the logic that
    determines what the latest lauchable browser version is, factoring
    in the currently loaded browser and whether stateful component
    builds will actually be loaded even if newer versions exist.

  - A single source for the latest launchable browser version allows
    for a consistent check to determine whether or not an update
    should be attempted. Previously this decision was tracked as
    an independent boolean on BrowserManager and separately via
    bespoke version-check logic in the version service. There were
    instances where these could get out of sync and cause a
    restart-update loop.

For more details see the doc below.

https://docs.google.com/document/d/1paR-Wacn0DIgRcZZUu0aUVzEJm_u607V5bLMz9Mf1QQ/edit?resourcekey=0-Zs9aS4wQ7wukeWcAX78LeQ#bookmark=id.lomqof6mlm5f

Bug: 1285382, 1373098
Change-Id: I59c6eee9642be3577cca24740eb3e9e5164af657
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4023853
Reviewed-by: Nancy Wang <nancylingwang@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1072527}