change type of max_bytes to ByteType

[leehinman]

What does this PR do?

This changes the type of MaxBytes in parsers to cfgtype.ByteType.

Why is it important?

Without this change MaxBytes in awss3 input could only be numbers even
though it was of type cfgtype.ByteType

This allows for both numbers and humanize values in the config files
for max_bytes

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
  - [ ] I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

How to test this PR locally

cd libbeat/reader/parser && go test

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[elasticmachine]

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Build stats

• Build Cause: Pull request #26699 updated

• Start Time: 2021-07-06T13:38:32.129+0000

• Duration: 131 min 15 sec

• Commit: 59c01df

Test stats 🧪

Test	Results
Failed	0
Passed	48592
Skipped	5395
Total	53987

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Test stats 🧪

Test	Results
Failed	0
Passed	48592
Skipped	5395
Total	53987

[v1v]

/test

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b max_bytes_bytesize upstream/max_bytes_bytesize
git merge upstream/master
git push upstream max_bytes_bytesize