Create test pattern for Spans

[alamb]

Part of #1548

Usecase

• We have added span information in Implement Spanned to retrieve source locations on AST nodes #1435

We would like to add span information through out the rest of the AST structures (see docs in #1549) and list on #1548

In order to support this feature reasonably, we need to be able to test the feature and avoid regressions

Proposal

I think we need some sort of span test.

I recommend

1. A new test binary like tests/sqlparser_spans.rs

Then add a test that

1. Parses a SQL string
2. Check the spans of the AST nodes match what is expected

I think we'll have to use judgement on how fine grained the location information
can / should be.

[alamb]

@lustefaniak , given your comments on

• locations: Add support for Spans with exact location of AST nodes #1480

We have an extensive internal test suite living in a downstream project using a fork of this library.

I wonder if you have any suggestions here (or maybe a code pointer for the downstream tests that we could possible start looking at?)