Rename scripts' modules_exp to modules_for_bom

[ivanvc]

What would you like to be added?

This is a follow-up on #18590 (comment). Currently, the function modules_exp defined in scripts/test_lib.sh is serving the only purpose of providing a list of modules for verifying and fixing the bill of materials (BOM).

etcd/scripts/test_lib.sh

Lines 199 to 203 in e094139

	function modules_exp() {
	for m in $(modules); do
	echo -n "${m}/... "
	done
	}

We should rename it from modules_exp to modules_for_bom for clarity and update the two instances where it is referenced:

1. scripts/test.sh:

   etcd/scripts/test.sh

   Lines 508 to 512 in 4f9cd33

   	function bom_pass {
   	log_callout "Checking bill of materials..."
   	# https://github.com/golang/go/commit/7c388cc89c76bc7167287fb488afcaf5a4aa12bf
   	# shellcheck disable=SC2207
   	modules=($(modules_exp))

2. scripts/updatebom.sh:

   etcd/scripts/updatebom.sh

   Line 15 in 4f9cd33

   modules=($(modules_exp))

Why is this needed?

To improve the code and clarity of the helper functions from the build and test scripts.

[ivanvc]

/assign @lekaf974

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In response to this:

/assign @lekaf974

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