package kit: Add pre-uninstall scripts feature.

Just like post-install scripts which run shortly after a package is
installed, pre-uninstall scripts are run just before a package is
removed. Implements enhancement #13427

* Fix script exit code handling vs script launch errors.
* Bump package and repo file version numbers due to new attribute,
unfortunately makes new .hpkg files not backwards compatible.
* Add pre-uninstall functionality, mostly cloning the post-install
except in a few places.
* Discover that _RunQueuedScripts() is never called, a future TODO:?
* Update package documentation for pre-uninstall scripts, and use of
the boot/post-install directory.

Change-Id: I45596255ce74bc102f6e5b606cbf83e4e4347a17
Reviewed-on: https://review.haiku-os.org/c/haiku/+/1504
Reviewed-by: Alexander G. M. Smith <agmsmith@ncf.ca>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

BTransactionIssue: String improvements

BTransactionIssue::ToString(): Fix some strings

package daemon: Rework error and issue propagation to client

* BDaemonClient: Move inner class BCommitTransactionResult to top level
and make it public.
* BCommitTransactionResult:
- Add a whole bunch of specific error code enum values. Such an error
code is now the primary error, as opposed to before where we would
mix status_t and enum value errors. There's a systemError property
of type status_t which may provide additional information, though
(depending on the primary error type).
- Remove the errorMessage property. Due to mapping all errors to the
specific error codes this is no longer necessary. Mixing such a
message with another error description is also not very helpful when
it comes to localization (still not supported, though).
- Add several properties (paths, strings, error codes) that serve as
arguments to the primary error and are used by FullErrorMessage().
- Add issues property, a list of instances of new class
BTransactionIssue. Those describe non-critical issues (e.g. failed
update of a settings file) that occurred in the process of
committing the transaction. Those issues should be presented to the
user by the package management program.
* Exception: Adjust to transport the BCommitTransactionResult
properties.
* CommitTransactionHandler, FsTransactions, Root, Volume: Adjust to
BCommitTransactionResult/Exception changes.
* CommitTransactionHandler: Now requires a BCommitTransactionResult to
which it adds the issues it encounters. The reply BMessage is no
longer needed, though.
* Volume: Refactor common code from the three methods that use
CommitTransactionHandler into new method _CommitTransaction.

BTransactionIssue: String improvements

BTransactionIssue::ToString(): Fix some strings

package daemon: Rework error and issue propagation to client

* BDaemonClient: Move inner class BCommitTransactionResult to top level
and make it public.
* BCommitTransactionResult:
- Add a whole bunch of specific error code enum values. Such an error
code is now the primary error, as opposed to before where we would
mix status_t and enum value errors. There's a systemError property
of type status_t which may provide additional information, though
(depending on the primary error type).
- Remove the errorMessage property. Due to mapping all errors to the
specific error codes this is no longer necessary. Mixing such a
message with another error description is also not very helpful when
it comes to localization (still not supported, though).
- Add several properties (paths, strings, error codes) that serve as
arguments to the primary error and are used by FullErrorMessage().
- Add issues property, a list of instances of new class
BTransactionIssue. Those describe non-critical issues (e.g. failed
update of a settings file) that occurred in the process of
committing the transaction. Those issues should be presented to the
user by the package management program.
* Exception: Adjust to transport the BCommitTransactionResult
properties.
* CommitTransactionHandler, FsTransactions, Root, Volume: Adjust to
BCommitTransactionResult/Exception changes.
* CommitTransactionHandler: Now requires a BCommitTransactionResult to
which it adds the issues it encounters. The reply BMessage is no
longer needed, though.
* Volume: Refactor common code from the three methods that use
CommitTransactionHandler into new method _CommitTransaction.