docs: add docs about x/auth/tx (backport #14021)

[mergify]

This is an automatic backport of pull request #14021 done by Mergify.
Cherry-pick of 6f329d7 has failed:

On branch mergify/bp/release/v0.47.x/pr-14021
Your branch is up to date with 'origin/release/v0.47.x'.

You are currently cherry-picking commit 6f329d70c.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   api/cosmos/crisis/module/v1/module.pulsar.go
	modified:   api/cosmos/crisis/v1beta1/tx.pulsar.go
	modified:   api/cosmos/crisis/v1beta1/tx_grpc.pb.go
	renamed:    api/cosmos/tx/module/v1/module.pulsar.go -> api/cosmos/tx/config/v1/config.pulsar.go
	modified:   baseapp/util_test.go
	modified:   docs/docs/core/05-encoding.md
	renamed:    docs/modules_category.json -> docs/docs/modules/_category_.json
	new file:   docs/docs/pkg/_category_.json
	modified:   docs/post.sh
	modified:   docs/pre.sh
	modified:   fuzz/README.md
	modified:   go.mod
	renamed:    proto/cosmos/tx/module/v1/module.proto -> proto/cosmos/tx/config/v1/config.proto
	modified:   server/grpc/grpc_web_test.go
	modified:   simapp/app_config.go
	modified:   simapp/app_v2.go
	modified:   simapp/go.mod
	modified:   tests/go.mod
	modified:   tests/integration/bank/keeper/deterministic_test.go
	modified:   tests/integration/genutil/gentx_test.go
	modified:   tests/integration/runtime/query_test.go
	modified:   testutil/configurator/configurator.go
	modified:   testutil/network/network.go
	modified:   x/README.md
	modified:   x/auth/README.md
	modified:   x/auth/migrations/legacytx/config_test.go
	modified:   x/auth/testutil/app_config.go
	new file:   x/auth/tx/README.md
	modified:   x/auth/tx/config.go
	renamed:    x/auth/tx/module/module.go -> x/auth/tx/config/config.go
	modified:   x/auth/tx/config_test.go
	renamed:    x/auth/testutilhelpers/tx/suite.go -> x/auth/tx/testutil/suite.go
	modified:   x/auth/vesting/README.md
	modified:   x/authz/testutil/app_config.go
	modified:   x/bank/app_test.go
	modified:   x/bank/simulation/operations_test.go
	modified:   x/capability/testutil/app_config.go
	modified:   x/crisis/types/tx.pb.go
	modified:   x/distribution/testutil/app_config.go
	modified:   x/evidence/testutil/app_config.go
	modified:   x/feegrant/testutil/app_config.go
	modified:   x/gov/simulation/operations_test.go
	modified:   x/group/testutil/app_config.go
	modified:   x/mint/testutil/app_config.go
	modified:   x/nft/testutil/app_config.go
	modified:   x/params/testutil/app_config.go
	modified:   x/slashing/testutil/app_config.go
	modified:   x/staking/testutil/app_config.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   api/cosmos/auth/v1beta1/query.pulsar.go
	both modified:   go.sum
	both modified:   simapp/go.sum
	both modified:   tests/go.sum
	both modified:   x/auth/types/query.pb.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[julienrbrt]

Let's wait until I tag API and update this PR to merge this.
Done.

[sonarcloud]

[cosmos-sdk-client-v2] Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[sonarcloud]

[cosmos-sdk-core] Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[sonarcloud]

[Cosmos SDK] Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

91.7% Coverage
0.0% Duplication