[BEAM-6318] Increase the amount of pip download retries to 10 from a default 5

[tvalentyn]

In BEAM-6318 we suspect that Beam test suites sometimes become flaky during PyPi outages, and we are exploring adding retries as a mitigation. This PR increases the number of retries used by pip from 5(default) to 10. In pip, retries happen with a back-off. I verified on a VM without internet access that with 10 retries pip attempts to download a package throughout 4 minutes, while first 5 attempts happen within 5 seconds.

If pip retry mechanism proves not sufficient to mitigate BEAM-6318, we can issue multiple calls to pip, also with a back-off.

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Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Samza	Spark
Go		---	---	---	---	---	---
Java
Python		---			---	---	---

[tvalentyn]

R: @aaltay