Remove Bundler::CompactIndexClient

Bundler now uses Gem::CompactIndexClient, so delete the duplicate
client and its unit specs. Coverage the specs had over the RubyGems
test suite moves to test-unit: available? boundaries, yanked-line
checksums, versions lines without a checksum, missing ETag headers
(#5463), invalid gzip responses, blank partial responses, an etag
written concurrently by another process, and non UTF-8 responses under
an ASCII default internal encoding. This also fixes two latent Bundler
bugs by inheriting the RubyGems behavior: an inverted debug message in
the info fetch skip path, and a NoMethodError on malformed Digest
headers.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: hsbt

Manifest.txt

@@ -53,11 +53,6 @@ lib/bundler/cli/pristine.rb
 lib/bundler/cli/remove.rb
 lib/bundler/cli/show.rb
 lib/bundler/cli/update.rb
-lib/bundler/compact_index_client.rb
-lib/bundler/compact_index_client/cache.rb
-lib/bundler/compact_index_client/cache_file.rb
-lib/bundler/compact_index_client/parser.rb
-lib/bundler/compact_index_client/updater.rb
 lib/bundler/constants.rb
 lib/bundler/current_ruby.rb
 lib/bundler/definition.rb