chore: make names of synthetics entities created in tests consistent

[pranav-new-relic]

In multiple tests used in the synthetics package which end up creating/updating/deleting Synthetic Monitors, Private Locations and Secure Credentials, the names of resources created are currently not consistent -

• Very few of them have a string that helps identify that the source of the entity is newrelic-client-go.
• A large number of them have no such identifier and simply have a mock.RandSeq(5) as the name of the entity.

This makes it difficult to track down redundant Synthetic entities in the account which may have not been deleted successfully owing to test failures or other similar reasons, and which would need to be cleaned up (given, in recent times, a large number of redundant monitors created by the client's test which remained and did not get deleted, led to the limit of Synthetic Checks getting breached).

Hence, this PR addresses a tiny change to all tests in the synthetics package - make the names of entities created uniform, with a identifier client-go-test that helps identify that the entities were created from newrelic-client-go's tests.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1d2c76f) 39.08% compared to head (489097c) 67.43%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1067       +/-   ##
===========================================
+ Coverage   39.08%   67.43%   +28.35%     
===========================================
  Files          82      100       +18     
  Lines        5133     5884      +751     
===========================================
+ Hits         2006     3968     +1962     
+ Misses       2977     1594     -1383     
- Partials      150      322      +172     

Flag	Coverage Δ
integration	58.53% <ø> (?)
unit	39.08% <ø> (ø)

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[pranav-new-relic]

All tests successful (link to integration tests) 👍 however, it is worth mentioning (for anyone seeing this PR in future) that one specific test, TestIntegrationListTags is very flakey - locally running this tests seems to cause no failure, but this fails in the CI quite frequently, and then, randomly passes in the next one or two test runs.

Merging this PR shortly as this is a minor change (expected to cause no change to feature behaviour) and since all tests have passed successfully.