feat(pack): ensure order of `PackChanged{Pre,}` events #40455

Problem: due to totally async install/update/checkout there is no
  guaranteed order of `PackChanged{Pre,}` events across different
  plugins. This might lead to conflicts when callback for some "main"
  plugin relies on features from "dependency" plugin: i.e. callback for
  "main" plugin can trigger before installing/updating "dependency"
  plugin. The installation order can be enforced by separate
  vim.pack.add() calls, but update/checkout can not.

Solution: Trigger events in bulk independently of async execution:
  - `PackChangedPre` before any action for all input plugins in order
    they are supplied. It will also trigger even if an action will fail.
  - `PackChanged` after all actions finished for all sucessfully
    affected plugins in order they are supplied.

  This also comes with a couple of side effect changes:
  - `PackChangedPre kind=delete` is now also triggered even if the
    delete won't be done. This makes it more aligned with `kind=install`
    and `kind=update`.
  - Force update (`:packupdate!`) and "udpate LSP action" now do two
    async steps: download/compute updates and apply them. This also
    results in two progress reports.
    This is mostly a by-product of the implementation (there has to be
    a pre-computation of target revision for all plugins before doing
    `PackChangedPre` in bulk before possibly applying an update), but I
    kind of like it more this way as it is more explicit of what's going
    on. If absolutely not acceptable, there might be some hacks to
    mitigate it at least in code action, but I'd keep it like this.

0 files changed, 0 insertions, 0 deletions