feat: support degree algorithm (#795)

[ArmxG]

What this PR does

This PR adds a built-in Degree graph algorithm (UDGA), as requested in #795.

For each vertex, it returns:

(id, in_degree, out_degree)

Approach

• Counts the incoming and outgoing edges for each vertex using context.loadEdges(EdgeDirection.IN/OUT).
• Since each vertex can calculate its own degree, the algorithm does not use message passing and finishes in a single iteration.
• Registers degree() in BuildInSqlFunctionTable, similar to the existing built-in algorithms such as KCore.

Tests

• Added gql_algorithm_degree.sql and the expected output file gql_algorithm_degree.txt.
• Verified the output on the test graph, including a vertex with an out-degree of 0.
• Added testAlgorithmDegree in GQLAlgorithmTest, following the existing algorithm test pattern.