[Filebeat] httpjson: Add replaceAll helper function

[andrewkroh]

What does this PR do?

replaceAll returns a copy of the string s with all non-overlapping instances
of old replaced by new.

Note that the order of the arguments differs from Go's strings.ReplaceAll to
make pipelining more ergonomic. This allows s to be piped in because it is
the final argument. For example,

[[ "some value" | replaceAll "some" "my" ]] // == "my value"

Why is it important?

This gives a simple way to manipulate a string in a template. The use case is fixing an incorrectly formatted nextlink value that an API (Trend Micro Vision One) is returning for pagination.

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.

Related issues

• Relates #123

[elasticmachine]

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

[elasticmachine]

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• Start Time: 2022-07-18T22:00:04.434+0000

• Duration: 76 min 26 sec

Test stats 🧪

Test	Results
Failed	0
Passed	2172
Skipped	166
Total	2338

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