chore: fix permissions of files generated in docker (cosmos#1276)

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## Overview

Currently, docker is executed with default privileges (as root), which
makes it hard to deal with files generated by `make proto-gen`. As a
workaround, files are copied to a new directory (to get correct access
rights), and the original directory is a part of .gitignore.

The solution consists of three improvements:
 - -u flag added to docker command to run as the current user
- XDG_CHACHE_HOME modified, to mitigate access permissions (it's picked
up by buf process inside container)
 - buf output directory is set properly, so there is no need for copying


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## Checklist

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- [x] New and updated code has appropriate documentation
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- [ ] Linked issues closed with keywords


<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

### Summary by CodeRabbit

- Chore: Updated the script used for generating protocol buffers. The
changes ensure that the script runs in a more secure and efficient
manner by using the current user's UID and GID, and by setting the cache
directory to a temporary location. This will help in maintaining the
cleanliness of the project directory and improve the overall development
experience. Please note that the copying of protocol buffer files to the
target directory has been removed, so you may need to adjust your
workflow accordingly.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

buf.gen.yaml

@@ -4,7 +4,7 @@ version: v1beta1
 plugins:
   # The name of the plugin.
   - name: gogofaster
-     # The the relative output directory.
-    out: proto/pb
+     # The relative output directory.
+    out: types/pb
     # Any options to provide to the plugin.
     opt: plugins=grpc,paths=source_relative

proto/gen.sh

@@ -7,8 +7,7 @@ TARGET_DIR=./types/pb
 cd $SCRIPT_DIR
 mkdir -p $TARGET_DIR
 rm -rf $TARGET_DIR/*
-docker run -v $PWD:/workspace --workdir /workspace tendermintdev/docker-build-proto sh ./proto/protoc.sh
+docker run -u $UID:$(id -g) -e XDG_CACHE_HOME=/tmp/.cache -v $PWD:/workspace --workdir /workspace tendermintdev/docker-build-proto sh ./proto/protoc.sh
 
-cp -r ./proto/pb/* $TARGET_DIR/
 
 rm -rf $TARGET_DIR/tendermint