MQE-1057: Update metadata filenames convention

[tomreece]

Need to update technical guidelines.

Related PRs to MFTF-3.0.0 develop branches:

• https://github.com/magento-pangolin/magento2ce/pull/234
• https://github.com/magento-pangolin/magento2ee/pull/109
• https://github.com/magento-pangolin/magento2b2b/pull/38
• https://github.com/magento-pangolin/inventory/pull/1
• <note: no pagebuilder changes required>
• Technical guidelines: MQE-1057: Update metadata filenames convention devdocs#6764

Build
https://m2build-ur.devops.magento.com/job/All-User-Requested-Tests/30315/

The above build has failures, but they are equivalent to the MFTF-3.0.0 branch failures.

[coveralls]

Coverage remained the same at 50.883% when pulling a406a6f on MQE-1057 into 3a18c6b on develop.

[soumyau]

Could see a couple more usages of -meta.xml in mftf. Can you please check if they need to be renamed as well -
MetadataGenerator.php => generateMetaDataFile, comment block of $filepath
MetadataGenUtil.php => __construct, comment block of $filepath

[tomreece]

Could see a couple more usages of -meta.xml in mftf. Can you please check if they need to be renamed as well -

Those files are outdated and unused. I did not touch these files because they should be removed from our framework. If I fix the comment, I have to fix the implementation of those which generate -meta.xml files and we never test that code.

Is it ok if I leave it as-is?