Remove prism pack parsing

It was never adopted by ruby or other implementations.
Ruby 4.1 may add new directives, so now is a good time to remove it.

It was actually never properly documented (just shows `Prism::Pack` with no methods)
so removing seems safe to do even now.

Ref
* ruby/prism#3909
* ruby/prism#3907

Author: Earlopain

common.mk

@@ -90,13 +90,11 @@ MAKE_ENC      = -f $(ENC_MK) V="$(V)" UNICODE_HDR_DIR="$(UNICODE_HDR_DIR)" \
 PRISM_BUILD_DIR = prism
 
 PRISM_FILES = prism/api_node.$(OBJEXT) \
-		prism/api_pack.$(OBJEXT) \
 		prism/diagnostic.$(OBJEXT) \
 		prism/encoding.$(OBJEXT) \
 		prism/extension.$(OBJEXT) \
 		prism/node.$(OBJEXT) \
 		prism/options.$(OBJEXT) \
-		prism/pack.$(OBJEXT) \
 		prism/prettyprint.$(OBJEXT) \
 		prism/regexp.$(OBJEXT) \
 		prism/serialize.$(OBJEXT) \

depend

@@ -21,7 +21,6 @@ module Prism
   autoload :InspectVisitor, "prism/inspect_visitor"
   autoload :LexCompat, "prism/lex_compat"
   autoload :MutationCompiler, "prism/mutation_compiler"
-  autoload :Pack, "prism/pack"
   autoload :Pattern, "prism/pattern"
   autoload :Reflection, "prism/reflection"
   autoload :Relocation, "prism/relocation"

lib/prism.rb

@@ -42,7 +42,6 @@ Gem::Specification.new do |spec|
     "docs/serialization.md",
     "docs/testing.md",
     "ext/prism/api_node.c",
-    "ext/prism/api_pack.c",
     "ext/prism/extension.c",
     "ext/prism/extension.h",
     "include/prism.h",
@@ -52,7 +51,6 @@ Gem::Specification.new do |spec|
     "include/prism/encoding.h",
     "include/prism/node.h",
     "include/prism/options.h",
-    "include/prism/pack.h",
     "include/prism/parser.h",
     "include/prism/prettyprint.h",
     "include/prism/regexp.h",
@@ -80,7 +78,6 @@ Gem::Specification.new do |spec|
     "lib/prism/mutation_compiler.rb",
     "lib/prism/node_ext.rb",
     "lib/prism/node.rb",
-    "lib/prism/pack.rb",
     "lib/prism/parse_result.rb",
     "lib/prism/parse_result/comments.rb",
     "lib/prism/parse_result/errors.rb",
@@ -133,7 +130,6 @@ Gem::Specification.new do |spec|
     "sig/prism/mutation_compiler.rbs",
     "sig/prism/node_ext.rbs",
     "sig/prism/node.rbs",
-    "sig/prism/pack.rbs",
     "sig/prism/parse_result.rbs",
     "sig/prism/parse_result/comments.rbs",
     "sig/prism/pattern.rbs",
@@ -146,7 +142,6 @@ Gem::Specification.new do |spec|
     "src/encoding.c",
     "src/node.c",
     "src/options.c",
-    "src/pack.c",
     "src/prettyprint.c",
     "src/prism.c",
     "src/regexp.c",