Support implicit type conversion from string to boolean

[dai-chen]

Description

Changes

1. Add missing cast function for byte and short: because after changes, cast function must exist for implicit conversion to the type.
2. Support implicit conversion from string to bool by wrapping original function builder during compile time. In particular, if there is mismatch between unresolved (user given) and resolved function signature, wrap argument(s) of "mismatched" type by cast function. Please see user manual and design doc below for more details.

Documentation

1. User manual: https://github.com/dai-chen/sql-1/blob/support-cast-bool-to-string/docs/user/general/datatypes.rst
2. Design doc: https://github.com/dai-chen/sql-1/blob/support-cast-bool-to-string/docs/dev/TypeConversion.md

TODO: Remove special case for conversion between numbers and fix all failed UTs.

Issues Resolved

#113

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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