Support package pattern for --deleted_packages

[pauldraper]

Description

This allows all BUILD/BUILD.bazel files in a tree to be ignored.

--deleted_packages=third_party/example/...

Motivation

Solves several possible uses.

1. Handle vendored sources that have non-Bazel BUILD files.
2. Select all files in an Bazel workspace for an E2E Bazel test, without interference from BUILD in that workspace.
3. Do "all files" operations, e.g. lint and formatting, by symlinking to the workspace, adding a BUILD with globs to that repo, and ignore package boundaries in that new repo.

While these are possible by explicitly listing individual packages: (1) That requires an extra script/process. (2) The list can get very, very long.

Note: This is different than .bazelignore or REPO.bazel ignore_directories. --deleted_packages still leaves file accessible, albeit without interpreting the packages.

Build API Changes

This change is backwards compatible, and consistent with Bazel package pattern syntax.

Resolves #28844.

Checklist

• I have added tests for the new use cases (if any).
• I have updated the documentation (if applicable).

Release Notes

RELNOTES[NEW]: --deleted_packages accepts a pattern (e.g. example/path/...) that recursively ignores packages.