Implement ExtractInfo

[rudolfix]

Background
extract step does not generate any execution / tracing info, let's fix that. Should not be started before #757 is implemented and common interface of all step infos is clear

Tasks

1. • implement ExtractInfo with asdict and asstr methods like the other infos. asdict must generate dlt friendly object that can be loaded into a relational structure, asstr must be friendly to our pipeline info command that displays traces
2. • extract step may extract many sources. each extracted source is a separate operation and ExtractInfo must collect all of them.
3. • implement all common fields as per refactor NormalizeInfo and LoadInfo #757

extract info should contain the following information
in extract info per source

• • source name and schema name (they must be identical - we'll enforce that see enforce schema and source name to be the same #758 ), load_id (see generate load_id in extract step #756 )
• • a DAG of selected resources (by name - they are unique). mind that source has a method that generates DAGs
• • for each source and resource a list of applied hints
• • for each resource collect metrics: the count of the items, number of written bytes, the counts of extracted items per table + bytes, user defined metrics (ticket icoming)
• • for each table: the list of extracted files and their sizes
• • elapsed time for each resource
• • resource state, source state (this should be optional, maybe extractor config)
• • resource arguments (if created with decorator) - we have that partially implemented!
• • source arguments (if created with decorator) - to be implemented

Implementation
You must be able to get all the data above after execution is finished. You must be able to collect partial info also when we have an exception during extract (info is part of exception)

users can add custom metrics to resources that will be part of extract info. please read #755 for some implementation hints. we can collect metrics in organized way even before custom metrics are added