Compile time support

[bobozaur]

Adds compile-time query macros and sqlx-exasol-cli, sqlx-cli like tool. Depends on launchbadge/sqlx#3889.

TODO:

• Get features in sync with sqlx and fix README and lib.rs
• Implement compile-time macros tests
• Implement sqlx-exasol-cli tests
• Look more closely into module organization since now we're re-exporting sqlx stuff
• Get rid of test_multi_statement_in_fetch test and adjust fetch_many to address Executor::fetch_many impl should error on arguments or persistence #34
• Get CI up to speed
• Get the publish workflow up to speed
• Check the type_checking (feature-types implementation, array types)
• Add support for bigdecimal and time crates
• Look into whether integer conversion to strings can be abstracted away
• Document the removal of ExaDataType::compatible in favor of TypeInfo::type_compatible
• Check whether ExaDataType::Null is actually useful since Exasol does not provide columns/parameters nullability
• Review supported data types to essentially allow the same data types for both compile time and runtime checks
• Review data type compatibility checks
• Review whether the Clone bound on ExaIter can be removed
• Document either usage of extern crate sqlx_exasol as sqlx; or using package in Cargo.toml to satisfy internal SQLx path qualifications
• Trim down Encode::produces usage where it's not adding any new info
• Look into implementing Encode/Decode for Json SQLx adapter
• Consider relaxing runtime length checks for various types, like ints
• Extend compile time tests to all supported owned and referenced types, including those wrapped in Option
• Document the removal of Encode for &mut [T]
• Consider renaming ExaIter to ExaParams
• Consider adding examples of general usage, ETL and using both sqlx-exasol and sqlx
• Consider dropping support for more exotic array types, keeping only slices, Vec, and fixed-sized arrays. Others can be wrapped in ExaIter
• Might have to drop decode support to strings for date time & decimals
• Update CHANGELOG

Closes #9 . Closes #34 .