Introduce grpc-native-debug gems containing debug symbol packages that complement the shared libraries shipped in pre-compiled binary gems.

Example package layout (1.60.0.dev is the "version" in this example):

$ find grpc-native-debug-1.60.0.dev-x86_64-linux/
grpc-native-debug-1.60.0.dev-x86_64-linux/
grpc-native-debug-1.60.0.dev-x86_64-linux/symbols
grpc-native-debug-1.60.0.dev-x86_64-linux/symbols/grpc-1.60.0.dev-x86_64-linux-ruby-3.0.dbg
grpc-native-debug-1.60.0.dev-x86_64-linux/symbols/grpc-1.60.0.dev-x86_64-linux-ruby-2.7.dbg
grpc-native-debug-1.60.0.dev-x86_64-linux/symbols/grpc-1.60.0.dev-x86_64-linux-ruby-3.2.dbg
grpc-native-debug-1.60.0.dev-x86_64-linux/symbols/grpc-1.60.0.dev-x86_64-linux-ruby-3.1.dbg
grpc-native-debug-1.60.0.dev-x86_64-linux/README.md
grpc-native-debug-1.60.0.dev-x86_64-linux/version.rb
grpc-native-debug-1.60.0.dev-x86_64-linux/platform.rb

Intended Usage

1. Fetch the grpc-native-debug package matching the RUBY_PLATFORM and version of the grpc gem being debugged. For example, if using grpc-1.60-x86_64-linux.gem, then fetch grpc-native-debug-1.60-x86_64-linux.gem.

2. Unpack the gem and find the symbols directory

3. Find the .dbg file matching the version of ruby being used (there are separate shared libraries for each ruby version so we also need separate .dbg files).

4. Use the symbols however needed. For example, to load in gdb one can follow https://stackoverflow.com/questions/30281766/need-to-load-debugging-symbols-for-shared-library-in-gdb.

Caveats

Why not just include debug symbols in the shared libraries we ship?

If we stopped stripping the shared libraries in binary gems today, we'd multiply the package size by an order of magnitude.

For example, on linux x86_64, a stripped and compressed grpc_c.so is about 4MB. The same thing unstripped is ~80MB. There's a further multiplying effect because we include ~4 different extension libraries in each binary gem - one for each ruby minor version. Considering that the linux x86_64 gem is ~18MB today, > 300MB would be a 10-20X size increase.