Documentation improvements.

Document that every model must have at least one input and one output.

Document graph constraints.

Elaborate a bit on "execution order".

Indicate how operands of different lifetimes are defined (or not).

Fix ANEURALNETWORKS_L2_NORMALIZATION documentation for output shape.

ANEURALNETWORKS_SPACE_TO_DEPTH has inconsistent names for dimensions.

ANEURALNETWORKS_PAD documentation doesn't clearly describe rank or
dimensions of output tensor.

Bug: 66478689
Bug: 67601776
Bug: 69631404
Bug: 79482779
Bug: 79539157
Bug: 79539928

Test: mma at tree root

Change-Id: I6227bea2a486d4b45022d590915e10a124d323d4
Merged-In: I6227bea2a486d4b45022d590915e10a124d323d4
diff --git a/current.txt b/current.txt
index cc86653..86f3b67 100644
--- a/current.txt
+++ b/current.txt
@@ -250,7 +250,7 @@
 5804ca86611d72e5481f022b3a0c1b334217f2e4988dad25730c42af2d1f4d1c android.hardware.neuralnetworks@1.0::IDevice
 12e8dca4ab7d8aadd0ef8f1b438021938e2396139e85db2ed65783b08800aa52 android.hardware.neuralnetworks@1.0::IExecutionCallback
 574e8f1499436fb4075894dcae0b36682427956ecb114f17f1fe22d116a83c6b android.hardware.neuralnetworks@1.0::IPreparedModel
-b07802a3433a9abec67a41525dc04eab9efb62760414e1d37e2f72cc5ae9cb8a android.hardware.neuralnetworks@1.0::types
+1a5ae9793223658174258b523763c557abad6fb917df0b8e3cc097fc89035811 android.hardware.neuralnetworks@1.0::types
 
 # Documentation fixups for b/78135149
 9e7a0b650d0e461ece2cfec0e1072abf8676f592b41a7fb48f01e88fc3c8f780 android.hardware.broadcastradio@1.0::types