Add Keypath to TextDelegate in order to have same cross platform behavior as iOS AnimationTextProvider.

[greggiacovelli]

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Is your feature request related to a problem? Please describe.
Currently if an animation is shared across Android and iOS the text layers are intercepted by their respective libraries differently. Android (TextDelegate) can only replace text with text that is named X, whereas iOS (AnimationTextProvider) will be able to look at either the Keypath and the text, by default (DictionaryTextProvider) will look for matching KeyPath that is named X. This creates a bit of a disconnect but prevents duplicate text among layers in an animation as well for android. Consider the following example set of layers

layer_1 with text "READ IT" // Let's say in context it's a commanding statement
layer_2 with text "READ IT" // Let's say in context it's a statement representing the past

By default the layers would be named the same as the text they contained. However this is just default. In the case where a content author would want to disambiguate the layers they can rename them. In this case, Android would not be able to replace the text on layer1 and layer2 independently. They would both be replaced with the same exact string. If TextDelegate were to be using to localize the text, it might be incorrect as text here could mean different things depending on context.

Describe the solution you'd like
I proposed #1931 as a possible solution. It merely exposes the KeyPath's name to the interface of TextDelegate to make an implementation possible that would address the above example.

Describe alternatives you've considered
We could also generate multiple animations that are organized specifically for Android vs iOS but that may defeat the overall purpose of the portable animation format. It's the current solution that we are going with but it's not ideal and very error prone.

Additional context
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