feat(ConfigProvider): Modify config merge to do replace instead of update for Specific tags

[jagan2221]

Modifying config merge functionality to do replace for collector_fields tag. Merge behaviour for other fields remains the same existing flow.

Why?
Collector tag edit behaviour change requirement

Things to note: This affects GlobProvider's behaviour too while merging config's for locally managed collectors. ie) collector_fields tag for locally managed collectors too will have this new behaviour while merging.

Need update in public doc which describes this merge behaviour. doc link

[rnishtala-sumo]

@jagan2221 is this PR going to change the default behavior? If so, could we add this behind a feature flag for the next release? We could keep the default behavior the same.

[jagan2221]

@jagan2221 is this PR going to change the default behavior? If so, could we add this behind a feature flag for the next release? We could keep the default behavior the same.

It only affected "collector_fields" key specifically, i think there won't be real use case where currently customer's use this key in multiple config files for locally managed collectors. Usually for locally managed collectors , customer's maintain this in sumologic.yaml right, so i feel there won't be a case for having this in another config file.
And we have explained this as a breaking change for corner case in release notes too. Your thoughts on this ?@rnishtala-sumo

[rnishtala-sumo]

@jagan2221 I think since this affects config merge behavior, its a big enough change to be behind a feature flag for the next release, where the customer needs to set the flag to use this feature. Then eventually we could let this be the default.

[jagan2221]

@rnishtala-sumo This is a feature which needs to be enabled by default for collector tag edit to work. If we make customers to enable this, then we need to rely on this flag status for tag edit feature to work/shown in UI.
Like we are enabling this feature in UI and rely on another flag in agent to enable it.