make Coder.getEncodedElementByteSize public to allow performance improvements in higher level coders

[stankiewicz]

Fixes #33620

Half of the sdk coders have getEncodedElementByteSize public because they are invoked outside of beam.sdk.coders package.
Some accumulators like ComposedAccumulatorCoder should have access to optimized methods for calculating size but due to it can be any Coder.
Optimized way of calculating size shouldn't be limited to Coders implemented in beam.sdk.coders only.
This change changes it to public and fixes all the coders in beam sdk.

This will break coders implemented in customer codebase requiring small patch to change visibility.

[stankiewicz]

Alternative to breaking change would be keeping things as is and moving problematic accumulator to sdk but it won't help if someone else writes problematic coder outside of beam.

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[stankiewicz]

I've seen this type of conditionhere. StructuredCoder doesn't enforce overriding getEncodedElementByteSize so I'm not sure if this is best practice. Ideally I would like to loop and invoke this method for every coder (extending CustomCoder/StructuredCoder/Coder) on the list. If underlying coder has default implementation, it will just serialize as is.

[robertwb]

I would remove the typecheck on StructuredCoder, just loop and add for every coder. The only downside is that there may be overhead constructing multiple CountingOutputStreams rather than creating one, but as you say there's no contract between StructuredCoder and implementing getEncodedElementByteSize.

Go ahead and remove the check in LengthPrefixCoder too, there's no benefit for ever skipping this attempt.

[stankiewicz]

@robertwb thanks, changed.

[robertwb]

I am a bit concerned about the backwards incompatibility implications of changing the visibility here. If we do need to call it from outside a Coder (which seems OK to me), what if we instead make a public static method on Coder that calls this?

[robertwb]

I would remove the typecheck on StructuredCoder, just loop and add for every coder. The only downside is that there may be overhead constructing multiple CountingOutputStreams rather than creating one, but as you say there's no contract between StructuredCoder and implementing getEncodedElementByteSize.

Go ahead and remove the check in LengthPrefixCoder too, there's no benefit for ever skipping this attempt.

[stankiewicz]

I am a bit concerned about the backwards incompatibility implications of changing the visibility here. If we do need to call it from outside a Coder (which seems OK to me), what if we instead make a public static method on Coder that calls this?

added static method, thanks for suggestions!