[NEMO-327] Fix skew handling for multi shuffle edge receiver

[sanha]

JIRA: NEMO-327: Fix skew handling for multi shuffle edge receive

Major changes:

• For the case that a vertex receives multiple shuffle edges, makes DataSkewPolicy collect metric data for the shuffle edges in a single metric aggregation vertex and optimize the edges at once.

Minor changes to note:

• Makes runtime pass receive multiple target edges.

Tests for the changes:

• Adds an integration test with the data skew policy for NetworkTraceAnalysis that has a join.

Other comments:

• N/A.

Closes #189

[johnyangk]

Thanks @sanha 👍