feat(policies): add UseOnlineResharding update policy

[prajwal-swiggy]

Issue https://github.com/awslabs/goformation/issues/610

Description of changes: Add support for specifying UseOnlineResharding UpdatePolicy for ElastiCache ReplicationGroup

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[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.01% :warning:

Comparison is base (976990f) 5.67% compared to head (b702c23) 5.66%. Report is 6 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #611 +/- ## ========================================= - Coverage 5.67% 5.66% -0.01% ========================================= Files 30 30 Lines 18019 18047 +28 ========================================= Hits 1022 1022 - Misses 16968 16996 +28 Partials 29 29 ``` | [Files Changed](https://app.codecov.io/gh/awslabs/goformation/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs) | Coverage Δ | | |---|---|---| | [cloudformation/all.go](https://app.codecov.io/gh/awslabs/goformation/pull/611?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs#diff-Y2xvdWRmb3JtYXRpb24vYWxsLmdv) | `0.00% <0.00%> (ø)` | |

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[rubenfonseca]

Great job, thank you so much!

[github-actions[bot]]

:tada: This PR is included in version 7.9.0 :tada:

The release is available on GitHub release

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