Make view a soft keyword

[dreamsmasher]

Issue To Be Solved

Function purity annotations were added in #1870 for Stable Cadence, allowing referentially-transparent functions to be annotated as such with the new view keyword.

We currently treat view as a hard keyword, which prevents it from being used as an identifier in any context. This is a problem, as the NFT contracts and many other on-chain contracts use it for arguments and variables, which breaks their code.

Suggested Solution

Make view a soft keyword in identifier position. This will require 1 token of lookahead in the parser when a view token is encountered - if it's followed by fun, then we know we're encountering a view function declaration or expression. Otherwise, it can be treated as an identifier. The list of soft keywords in the Stable Cadence changelog will also need to be updated.

Tasks:

• Extend the parser
• Update documentation and changelogs