Release v0.7.0

This release is primarily focused on security hardening and dead code elimination.

Fixes

• Limit the number of characters that may be read when attempting error recovery (635951c)
• Set the default comprehension iteration limit to 10000 (83fb851)
• Check all arithmetic operations and type conversions for overflow (99ebd43)
• Reject Timestamp values outside the string-expressible range
• Reject Duration values which cannot be expressed within an int64 value
• Heap buffer overrun for specialized binary and ternary operators (dfe31a4)
• Ensure only valid map keys are supported in CreateStruct (3261a58)

Cleanups

This release also removes dependencies on the v1beta1 protos and deletes a lot of
related code which was otherwise used within CEL.