feat: Add support for TCP healthcheck

[ps-occrp]

This adds support for TCP health checks and fixes #129 , #258 and #272

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[imrannayer]

@ps-occrp can you plz add it to autogen and execute make build?
You can find details on contribution guidelines here

[ps-occrp]

@imrannayer done! Thanks for the hint!

[imrannayer]

@ps-occrp seems like tcp_health_check block hasrequest, response, port_name, proxy_header and port_specification. Can you plz add them in backends variable healthcheck section as optional and use them?
It seems like we are also missing healthcheck parameters for other healthcheck. Can you plz add them too?

[ps-occrp]

@imrannayer Thanks for picking this, I have added this parameters.

[imrannayer]

/gcbrun

[imrannayer]

@ps-occrp can u also add parameters in variables.tf file.

[ps-occrp]

@imrannayer done, I have additionally added optional missing parameters in other types of health checks to keep them all in sync.

[imrannayer]

/gcbrun