[pkg/ottl] New function SubSlice

[kaisecheng]

Component(s)

pkg/ottl

Is your feature request related to a problem? Please describe.

Currently, OTTL does not have a function to sub-slice a slice with a given start and end indices slice[start:end].

Describe the solution you'd like

1. Add SubSlice(target, start, end) converter and returns a new slice.
   target : any type of slice
   start : the starting index of the sublist (inclusive)
   end : the ending index of the sublist (exclusive)

2. Support Go's slice expressions syntax in ottl
   target[start:end]
   target[:end]
   target[start:]
   Following go slice expression, start and end can not be negative integer

Supporting (1) would be very helpful, (2) is cool to have it.

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• pkg/ottl: @TylerHelmuth @evan-bradley @edmocosta

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[axw]

Sounds sensible, and in line with the existing Substring converter. I wonder if this should be part of the language grammar, but I guess it's probably not worth it.