What would you like to be added?

This is a follow-up on #20850 (comment).

Currently, our Bash scripts follow a custom convention of defining the Makefile targets as "passes" that are in the scripts/{test,build,etc}.sh files. This custom (and undocumented) way of maintaining the scripts is difficult to follow by new contributors. Because of this, we currently don't have a standard and have a lot of duplication in our Makefile, spread across different files, and approaches to run these targets/functionality.

Examples of fragmented architecture

1. Custom "PASSES" framework:

   etcd/Makefile

   Lines 109 to 111 in 855c9ba

   	.PHONY: verify-bom
   	verify-bom:
   	PASSES="bom" ./scripts/test.sh

2. Executing a Bash script:

   etcd/Makefile

   Lines 229 to 231 in 855c9ba

   	.PHONY: sync-toolchain-directive
   	sync-toolchain-directive:
   	./scripts/sync_go_toolchain_directive.sh

3. Embedded scripts in the Makefile target:

   etcd/Makefile

   Lines 171 to 178 in 855c9ba

   	YAMLFMT_VERSION = $(shell cd tools/mod && go list -m -f '{{.Version}}' github.com/google/yamlfmt)
   	.PHONY: fix-yamllint
   	fix-yamllint:
   	ifeq (, $(shell command -v yamlfmt))
   	$(shell go install github.com/google/yamlfmt/cmd/yamlfmt@$(YAMLFMT_VERSION))
   	endif
   	yamlfmt -conf tools/.yamlfmt .

We want to simplify and standardize this, without creating a difficult custom framework to implement and maintain.

Why is this needed?

To improve the maintainability of our Bash scripts.