Create an MSRV policy in this crate

[alamb]

TLDR woudl be:

1. Define a MSRV policy (maybe copy the existing DataFusion one)
2. Implement some sort of CI check (again can copy / reuse the datafusion one if we want)

          🤔  interestingly we don't seem to have an MSRV policy in this crate (at least not that I could find in https://github.com/apache/datafusion-sqlparser-rs/blob/main/README.md) 

We do have such a thing in DataFusion here: https://github.com/apache/datafusion?tab=readme-ov-file#rust-version-compatibility-policy

Maybe it is worth considering adding some documentation / policy in the sqlparser crate too 🤔

Originally posted by @alamb in #1736 (comment)

[mvzink]

From looking into #1612, some test code uses associated type bounds (stabilized in 1.79). It could be rewritten if an earlier MSRV is desired (1.75 worked without it). That's moot if following a more progressive policy like DataFusion though.

[alamb]

From looking into #1612, some test code uses associated type bounds (stabilized in 1.79). It could be rewritten if an earlier MSRV is desired (1.75 worked without it). That's moot if following a more progressive policy like DataFusion though.

I don't have a strong preference -- I think keeping sqlparser simple / easy to embed sounds like a good idea but all the projects I care about use newer versions of rust 🤷

Hopefully others can chime in with their points of view