chore!: split `ValidationError` from `MaxSizeError`; `validate` and `max_serialized_size` made `BorshSchemaContainer`'s methods

[dj8yfo]

• [x] summary of changes:
  • [x] most of max_serialized_size code moved from borsh/src/schema_helpers.rs to borsh/src/schema/container_ext/max_size.rs
  • [x] max_serialized_size made a method of BorshSchemaContainer
  • [x] borsh::MaxSizeError moved to borsh::schema::SchemaMaxSerializedSizeError
  • [x] SchemaMaxSerializedSizeError::MissingDefinition -> SchemaMaxSerializedSizeError::MissingDefinition(Declaration)
  • [x] is_zero_size private function tries to detect recursion too, its return type changed to Result<bool, ()> (Err on recursive call)
  • [x] MaxSizeError::ZSTSequenceNotArray check and enum variant split into separate types and module borsh/src/schema/container_ext/validate.rs

  • [x] validate method of BorshSchemaContainer

    split

    pub enum MaxSizeError {
    Overflow,
    Recursive,
    MissingDefinition,
    ZSTSequenceNotArray,
    }

    into

    pub enum MaxSizeError {
    Overflow,
    Recursive,
    MissingDefinition,
    }

    and

    pub enum ValidateError {
    /// sequences of zero sized types of dynamic length are forbidden by definition
    /// see <https://github.com/near/borsh-rs/pull/202> and related ones
    ZSTSequence,
    }

[dj8yfo]

a valid alternative might be to remove second commit and newly added module borsh/src/schema/container_ext/validate.rs, and just remove MaxSizeError::ZSTSequenceNotArray variant and corresponding check