expression.svg: add IS [ NOT ] predicate bool args

Summary

• expression.svg: add IS [ NOT ] predicate bool args

Address changes from:

• picodata@4fb3d35b
• sbroad@f84401ec

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• Close #391 (closed)
• Cherry-pick to: none
• Staging: https://docs.binary.picodata.io/picodata/asabirov_update_expression_svg/reference/sql/select/#expression