Add Dynamic Type

[SpencerTorres]

Note: There are some server-side bugs that need to be fixed/merged, including a protocol update. However, this PR can still be reviewed as-is.

Summary

Implement Dynamic column type. Partially resolves #1430.

Usage

As for usage, this is the same as clickhouse.Variant, with the addition of an alias type called clickhouse.Dynamic. See Variant PR for more details on how these types work (#1453).

Since the Dynamic type starts as a blank Variant, it is best to append using clickhouse.NewDynamicWithType(value, "ClickHouseTypeName") so the underlying column can be created correctly. If a type isn't specified, a type inference function is used, but this may not always work as intended.

Examples are included in examples folder.

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added

[jkaflik]

API is pretty much the same as for Variant. Looks good, but might have the same concerns for type access functions as for Variant. How do you want to proceed with these PRs?

[SpencerTorres]

Included fixes/nits from the Variant PR, including adding tests for std sql. Also added a minimum server version check for the examples since that was causing test failures.

I still expect some server side changes to the Dynamic format in the future, but this should be ready to review/merge as is