Update system tests commands to build elastic-agent containers

[mrodm]

Proposed commit message

Update how system tests build the elastic-agent containers used in system tests.
Add parameter -y in the step in charge of updating packages to assume yes to all questions:

sh-5.1# microdnf update --help-all
Usage:
  microdnf [OPTION?] upgrade [PACKAGE?] - Upgrade packages

Help Options:
  -h, --help                    Show help options
  --help-all                    Show all help options
  --help-global                 Show global help options

Global Options:
  --assumeno                    Automatically answer no for all questions
  -y, --assumeyes               Automatically answer yes for all questions
...

Adding this parameter avoids being stuck the Buildkite steps waiting for confirmation as it happened in this build:

• https://buildkite.com/elastic/integrations/builds/33662#019a5038-5237-4777-83bd-e2b3683435e3/855-2330

#8 2.499 Transaction Summary:
#8 2.499  Installing:        1 packages
#8 2.499  Reinstalling:      0 packages
#8 2.499  Upgrading:         8 packages
#8 2.499  Obsoleting:        0 packages
#8 2.499  Removing:          0 packages
#8 2.499  Downgrading:       0 packages
#8 2.499 Is this ok [y/N]: 

This flag was already present in the system tests of the oracle package:

integrations/packages/oracle/data_stream/memory/_dev/test/system/test-memory-config.yml

Lines 13 to 16 in a8fcb8e

	elif grep -q "Red Hat" /etc/os-release ; then
	microdnf update -y
	microdnf install -y libaio wget unzip
	microdnf clean all

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.
• I have verified that any added dashboard complies with Kibana's Dashboard good practices

Author's Checklist

• [ ]

How to test this PR locally

cd packages/system
elastic-package stack up -v -d --version 9.2.0
elastic-package test system -v --data-streams auth

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: f028c16

cc @mrodm

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