Tests for closing the client are failing since a new client object is
created on every operation that uses the generated (v2) layer. This
changeset fixes it by moving the v2 client creation to
`testproxy/services/create-client.js` alongside the veneer client
creation.

Every command using the v2 layer is updated to read the client from the
client map instead of creating a new instance.

Three previosly failing tests are now passing with this fix:
- TestCheckAndMutateRow_Generic_CloseClient
- TestMutateRow_Generic_CloseClient
- TestReadModifyWriteRow_Generic_CloseClient

* Add npm run compile to the testproxy command

The test proxy references the compiled client library code. Every time the test proxy is run, we want it to reflect the source code so that as we develop we don’t get confused about what gets observed.

* feat: Add npm run compile to the testproxy command

* Always set the retry attempt to 0 for now

If the retry attempt is greater than 1 then a library called retryRequest creates a large delay. If we force the retry count to be 0 then we skip this delay and the requests run in the required timeline.

* fix: Always set the retry attempt to 0 for now

Source-Link: googleapis/synthtool@3602660
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest@sha256:e6d785d6de3cab027f6213d95ccedab4cab3811b0d3172b78db2216faa182e32

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

The client should still have the opportunity to retry after only a few retriable errors.

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>