[processor/filter] Create With*Functions factory options to register custom OTTL funcs programatically.

[franciscovalentecastro]

Description

Create With*Functions factory options to provide custom OTTL functions for logs, metrics or traces to the resulting processor. Also created the "exported" Default*Functions functions that can be used to provide a "subset" of the default functions used in the filter processor.

Some details and context about this PR :

• To create a custom filter processor the user needs to create a NewFactory providing the custom OTTL functions.
• The same change was done in the transformprocessor : [processor/transform] Create With*Functions factory options to provide custom OTTL funcs programatically. #39966.
• This is a result of the discussion in this thread : [processor/transform] Create Additional*Funcs config properties to provide additional OTTL funcs programatically. #39641 (comment) .
• This is intended for developers of Opentelemetry Collector Distributions.

Usage

The factory options can be used like the following example :

NewFactoryWithOptions(
	WithLogFunctions(filterprocessor.DefaultLogFunctions()),
	WithLogFunctions([]ottl.Factory[ottllog.TransformContext]{FunctionOne, FunctionTwo, ...}),
	WithLogFunctions([]ottl.Factory[ottllog.TransformContext]{FunctionThree, FunctionFour, ...}),
)

Link to tracking issue

• [processor/filter] Register programatically custom OTTL funcs in the filter processor. #40948

Testing

• Added unit tests for the modified methods and functions.

Documentation

• Added comments to the new With*Functions, Default*Functions and NewFactoryWithOptions functions.

[franciscovalentecastro]

Following up the review request @TylerHelmuth @boostchicken @mwear.

[edmocosta]

It looks good to me. API is consistent with the transform processor one (#39698), and it worked well on my local tests. Great work @franciscovalentecastro!

@evan-bradley, you might be interested on taking a look at this one considering you also reviewed the transform processor changes :)

[evan-bradley]

Sorry for the delayed review, this looks good to me. Thanks for your patience @franciscovalentecastro.