Revisit reserved identifiers

[kazimuth]

Currently I've removed reserved identifiers, this should be reworked somehow before 1.0

[bfops]

Adding this to 1.0 release

[bfops]

This is a breaking-ish change (because users may have used a word that we might end up deciding to reserve).

[gefjon]

See https://github.com/clockworklabs/SpacetimeDBPrivate/blob/master/proposals/0026-module-and-sdk-api/02-physical-queries.md#reserved-column-and-index-accessor-names and https://github.com/clockworklabs/SpacetimeDBPrivate/blob/master/proposals/0026-module-and-sdk-api/05-user-defined-reducers.md#reserved-reducer-names . We have no plans to reserve any other words at this time. Notably we do not want to reserve the words reserved by the SQL spec.

[bfops]

Let's also enforce this in the rust macro system. (It's already done in C#)

[gefjon]

We think we can get this in as a "bugfix" down the line, even though it will technically be a breaking change. We definitely can't get it into 1.0.