Provide error details through payload fields

Related dev. issue(s): https://github.com/tarantool/tarantool/issues/9108, https://github.com/tarantool/tarantool/issues/6166

Product: Tarantool
Since: 3.1
Root document: https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_error/
SME: @ nshy

Details

Now Tarantool error details are available as payload fields (which
in turn can be accessed as error object fields). For example:

tarantool> e = box.error.new(box.error.SPACE_EXISTS, 'some space')
tarantool> e.message
---
- Space 'some space' already exists
...
tarantool> e.space
---
- some space
...

One can introspect the details using error:unpack():

tarantool> e:unpack()

• space: some space
  code: 10
  base_type: ClientError
  type: ClientError
  message: Space 'some space' already exists
  trace:
  • file: '[string "e = box.error.new(box.error.SPACE_EXISTS, ''so..."]'
    line: 1
    ...
    Requested by @ nshy in https://github.com/tarantool/tarantool/commit/7410a4f0f29114bda675e8bffe4eca611e85c3f4.

Open the root box_error documentation and compare its current coverage with the payload-field and error:unpack() examples in this issue. Document access to error details and introspection, then verify that the examples accurately describe the Tarantool 3.1 behavior.