struct fidl_table_t

Tables are 'flexible structs', where all members are optional, and new

members can be added, or old members removed while preserving ABI

compatibility. Each table member is referenced by ordinal, sequentially

assigned from 1 onward, with no gaps. Each member content is stored

out-of-line in an envelope, and a table is simply a vector of these envelopes

with the requirement that the last envelope must be present in order

to guarantee a canonical representation.