ExecNode: Remove basic_block_id.
ExecNode: Remove basic_block_id.

This field was never used, and this saves 32 bytes from each ExecNode.

Change-Id: I527801e81ed02da75711a33f6cf865371e5d0b66

giosalv/526-aladdin,giosalv/526-aladdin,giosalv/526-aladdin,giosalv/526-aladdin