Currently, we delegate the work of serializing extensions to serializers in
case of known extensions. In case of unknown extensions we try to convert
them from Lua using the serialization and string conversion metamethods.

However, there are cases where we would prefer to do the serialization in
Lua instead of delegating to serializers. Let's always try to serialize
extensions first using Lua via `luaL_convertfield`, and, if it fails, or
the conversion returns an extension again, fallback to the serializers.

Needed for tarantool#9105

NO_CHANGELOG=<refactoring>
NO_DOC=<refactoring>
NO_TEST=<refactoring>

Currently, the error object's `__serialize` metamethod and the Lua
serializer only display the `message` field omitting all other potentially
useful fields.

Let's call the error object's `__serialize` metamethod from the Lua
serializer and call `error:unpack` from the `__serialize` metamethod to
display all other error object fields. This will transparently allow to
display the whole error stack (i.e., the cause chain).

Let's make the error object's  `__tostring` metamethod return the `message`
field followed by a whitespace and the rest of the fields encoded to JSON.
Let's print the error stack (i.e., the cause chain) on separate lines.

Since this change may potentially break existing users, let's add a new
`box_error_serialize_verbose` option to `compat` to retain old behavior,
and disable the new behaviour by default. Let's also retain the old
behaviour for the MsgPack serializers unconditionally.

Closes tarantool#9105

@TarantoolBot document
Title: Document increased error serialization verbosity
Product: Tarantool
Since: 3.1
Root documents: https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_error/
and https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_error/error
and https://tarantool.io/compat/box_error_serialize_verbose

[Link to the design document](https://www.notion.so/tarantool/Error-subsystem-improvements-90faa0a4714b4143abaf8bed2c10b2fc?pvs=4#072087684e094ea28cba88002236178a)

Please add a new https://tarantool.io/compat/box_error_serialize_verbose
page for the `box_error_serialize_verbose` compatibility option.