feat(meta): actor placement rule and dispatcher refactor

[skyzh]

Signed-off-by: Alex Chi iskyzh@gmail.com

What's changed and what's your intention?

• Remove ExchangeNode before fragment -> actor stage. As now fragments might have multiple dispatchers, information of exchange node is not useful anymore. Dispatch strategy is now recorded in FragmentEdge.
• Prepare for actor placement rule implementation. We need to ensure some actors stay on the same worker node. Now we add this field, set this field according to FragmentEdge. Will later add logic to enforce such rule.

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

ref #719

[yezizp2012]

LGTM！

[codecov]

Codecov Report

Merging #1843 (4ed695e) into main (c1c7440) will decrease coverage by 0.02%.
The diff coverage is 72.02%.

@@            Coverage Diff             @@
##             main    #1843      +/-   ##
==========================================
- Coverage   70.86%   70.84%   -0.03%     
==========================================
  Files         609      610       +1     
  Lines       79632    79689      +57     
==========================================
+ Hits        56431    56452      +21     
- Misses      23201    23237      +36     

Flag	Coverage Δ
rust	70.84% <72.02%> (-0.03%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/meta/src/model/stream.rs	53.57% <ø> (ø)
src/meta/src/stream/graph/fragment_graph.rs	96.94% <ø> (ø)
src/meta/src/stream/rewrite/delta_join.rs	0.00% <0.00%> (ø)
src/meta/src/stream/stream_manager.rs	72.50% <ø> (ø)
src/meta/src/stream/graph/stream_graph.rs	66.66% <72.91%> (-0.52%)	⬇️
src/meta/src/stream/fragmenter.rs	82.95% <73.33%> (-6.10%)	⬇️
src/meta/src/stream/scheduler.rs	97.20% <100.00%> (+0.03%)	⬆️

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