[CI] Set MODULE per relevant stage

[v1v]

#18741 was done but the regex in place is such a generic one that did not filter per module.

For instance, given the changeset:

CHANGELOG.next.asciidoc
NOTICE.txt
auditbeat/module/auditd/audit.go
auditbeat/module/auditd/config_linux.go
go.mod
go.sum

The current value for the environment variable MODULE is 'auditd' when running the Integration tests stage for the metricbeat, when the expected output should be ''

Test Scenarios

The below test scenarios should help to identify what the behaviour should be:

Single module changeset

When changeset:

CHANGELOG.next.asciidoc
NOTICE.txt
auditbeat/module/auditd/audit.go
auditbeat/module/auditd/config_linux.go
go.mod
go.sum

Then:

• auditbeat should set the MODULE to auditd
• metricbeat should set the MODULE to ''

Multi module changeset

When changeset:

CHANGELOG.next.asciidoc
NOTICE.txt
auditbeat/module/system/system.go
auditbeat/module/auditd/config_linux.go
go.mod
go.sum

Then:

• auditbeat should set the MODULE to ''
• metricbeat should set the MODULE to ''

single module changeset in multiple beats

When changeset:

CHANGELOG.next.asciidoc
NOTICE.txt
auditbeat/module/auditd/config_linux.go
metricbeat/module/system/system.go
go.mod
go.sum

Then:

• auditbeat should set the MODULE to auditd
• metricbeat should set the MODULE to system

multiple module changeset in multiple beats

When changeset:

CHANGELOG.next.asciidoc
NOTICE.txt
auditbeat/module/system/system.go
auditbeat/module/auditd/config_linux.go
metricbeat/module/system/system.go
metricbeat/module/logstash/connection/connection.go
go.mod
go.sum

Then:

• auditbeat should set the MODULE to ''
• metricbeat should set the MODULE to ''