[pkg/ottl] Add OTTL String Conversion Function

[Mrod1598]

Component(s)

pkg/ottl

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

Currently, when trying to convert a value from a float to string the only way I've seen to convert a number value to a string is to use the Concat function.

example parser using OTTL to convert a float into epoch time:

    transform/logging-0__processor1__logs:
        error_mode: ignore
        log_statements:
            - context: log
              statements:
                - set(cache["split"], Split(Concat([attributes["test"]],""), "."))
                - set(cache["seconds"], Concat([cache["split"][0], "s"], ""))
                - set(cache["fractional"], Concat([cache["split"][1], "ms"], ""))
                - set(time, Time("1970-01-01T00:00:00.000000+0000", "%Y-%m-%dT%H:%M:%S.%f%z") + Duration(Concat([cache["seconds"], cache["fractional"]], ""))) 

In the first set function, To ensure we can split on attributes["test"], with the value of 1234456.1234546, representing s.ms, we have to Call Concat to change it from a float to a string.

Describe the solution you'd like

A new function called String takes in a value and converts it into a string if possible.

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• pkg/ottl: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

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Pinging code owners:

• pkg/ottl: @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[TylerHelmuth]

This is a duplicate of #27867.