[pkg/ottl] Conflict resolution strategy for set function

[michalpristas]

Description:
Added conflict resolution strategy option for set function.
Available behaviors are:

• upsert: Is the default behavior. This setting results in creating field in case it's missing or updating existing value.
• update: This setting updates only existing value. In case value is missing no action is taken.
• insert: Creates a new field in case it's not present. In case field is already present no action is taken.
• fail: Similar to insert creates a field in case it's missing but returns an error otherwise.

ending up with following signature: set(target, value, [Optional] conflict_resolution_strategy) making sure current signature still works.

Link to tracking Issue:
#31808

Testing:
Mostly updated unit test to cover new functionalities, verify current behavior is kept as default and UT for testing default values behavior for cases when field is present but unset or containing zero value

Documentation:
updated pkg/ottl/ottlfuncs/README.md

[michalpristas]

if we have something better for this please let me know. i see following pattern repeated for many use cases

[codeboten]

Pinging code owners @TylerHelmuth @kentquirk @bogdandrutu @evan-bradley

[TylerHelmuth]

I am currently stuck on this thought we're discussing in the issue. Since OTTL can use Where clauses to handle conflict, I want to make sure the ergonomics of the conflict resolution is better than the Where clause.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[github-actions]

Closed as inactive. Feel free to reopen if this PR is still being worked on.