feat: expose more BCS helpers

[jjleng]

Description

Add more BCS helpers and expose them. This would simplify the usage of BCS. e.g.

  const serializer = new Serializer();
  serializer.serializeU32(123);
  const bytes = serializer.getBytes();

can be reduced to const bytes = bcsSerializeU32(123);

Test Plan

Added unit tests

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This change is 

[jjleng]

Are there deserialize matching functions too?

These bcsSerializeXXXX are used when submitting transactions. We can add some deserialization helpers if needed when we deserialize the payloads from Daniel's new BCS endpoints.

[github-actions[bot]]

:white_check_mark: Forge test success on 3009de26a44767cf8c59f90baac564df70c3067f

all up : 4958 TPS, 2223 ms latency, 3000 ms p99 latency,no expired txns

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