Proto/Michelson: Double type size limit

Context

See #1681 (closed). This MR implements the solution "Increase the limit (double it + 1), to make sure everything that passed before still passes now." As pointed there, "The main question is: why do we have this limit in the first place? Where is it used to prove something won't explode?"; @klakplok: any clue?

Manually testing the MR

• create a Granada mockup config

$ alias mockup_client='tezos-client --mode mockup --base-dir /tmp/mockup'
$ rm -rf /tmp/mockup
$ mockup_client --protocol PtGRANAD create mockup

• originate a contract with a big parameter type (size between 500 and 1000) and a big storage type (same size range)

$ mockup_client --protocol PtGRANAD originate contract test_big_type transferring 0 from bootstrap1 running [test_big_type.tz](/uploads/32c7113bd2ded6846546c9234cd24e52/test_big_type.tz)test_big_type.tz --init None --force --burn-cap 1

• check that the contract works on Granada

$ mockup_client --protocol PtGRANAD transfer 0 from bootstrap1 to test_big_type --arg None

• migrate the mockup config to Alpha

$ mockup_client migrate mockup to ProtoALphaALphaALphaALphaALphaALphaALphaALphaDdp3zK 

• call the contract on proto Alpha

$ mockup_client --protocol ProtoALpha transfer 0 from bootstrap1 to test_big_type --arg None

This should fail on master (with the error message "At (unshown) location 455, type exceeded maximum type size (1000).") and succeed on this branch.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, the Development Version section of CHANGES.md for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR