[Backend][SystemC] Stratus HLS Codegen Backend Support (Re-opened)

[zzzDavid]

Stratus HLS SystemC Backend Support

This PR implements the Stratus HLS SystemC backend, separating the backend implementation from issue fixes in the previous PR #375 .

Usage Example:

SystemC backend supports both string and platform backend specifications.

# Legacy string specification
code = hcl.build(s, target='shls')

# Platform specification
target = hcl.Platform.cadence_stratus
target.config(compiler="stratus_hls", project="vta_stratus_project", mode="csim")
f = hcl.build(s, target)

The platform specification has four modes:

• debug: return code string
• csim: call Stratus HLS and run c simulation
• cosim: call Stratus HLS and run RTL-C co-simulation
• power call Stratus HLS and report ASIC power analysis results

[zzzDavid]

@hecmay @chhzh123 Hi guys, could you start reviewing this PR? Hopefully we can get it merged this week before Thursday?