Add glob template helper function

[kcreddy]

The existing file template function reads a file from a full path. For example: {{file ./files/sample.csv}}
But at times, we want the ability to read all files from a folder when file name matches a pattern.
Example, when running integration system benchmarks¹, the corpus data generator tool creates sample data file with random suffix in its name ². The full name is not known, thus it cannot be read using file template function.

Enhancement:
Add glob function template function which can read multiple files matching a pattern.
Example usage: {{glob ./files/corpus-*}}

Footnotes

1. https://github.com/elastic/elastic-package/blob/main/docs%2Fhowto%2Fsystem_benchmarking.md ↩

2. https://github.com/elastic/elastic-package/blob/b2d0ec808c504a2c6e8bc9fefa6fff866c208c8b/internal/benchrunner/runners/system/runner.go#L589 ↩