feat: add getLogs() and getLogsStream()

[stephenplusplus]

RE: #550

This adds a new method, logging.getLogs() and logging.getLogsStream() using the logs.list API: https://cloud.google.com/logging/docs/reference/v2/rest/v2/logs/list

[stephenplusplus]

Using getLogs() and a naming convention consistent with the other test resources, we can clean up all test logs that are matched after each test run.

[codecov]

Codecov Report

Merging #692 into master will increase coverage by 0.56%.
The diff coverage is 91.11%.

@@            Coverage Diff             @@
##           master     #692      +/-   ##
==========================================
+ Coverage   68.24%   68.81%   +0.56%     
==========================================
  Files          36       36              
  Lines       10604    10828     +224     
  Branches      174      189      +15     
==========================================
+ Hits         7237     7451     +214     
- Misses       3366     3376      +10     
  Partials        1        1

Impacted Files	Coverage Δ
samples/logs.js	60.61% <10%> (-3.73%)	⬇️
src/index.ts	99.55% <99.02%> (-0.1%)	⬇️
src/sink.ts	98.86% <0%> (+0.56%)	⬆️
src/v2/logging_service_v2_client.js	94.02% <0%> (+0.64%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a8d587f...201c8cb. Read the comment docs.

[JustinBeckwith]

LGTM, but please let @bcoe have a look too.

[JustinBeckwith]

If this got embedded in cloud.google.com, the code inside of the region tag would have a top level await. That means folks couldn't reasonably copy and paste the sample without making changes. Instead, can we follow a model that introduces an async wrapper method? For Example:

async function listLogsMain() {
  // [START logging_list_logs]
  // Imports the Google Cloud client library
  const {Logging} = require('@google-cloud/logging');
  
  // Creates a client
  const logging = new Logging();

  async function listLogs() {
    const [logs] = await logging.getLogs();
    console.log('Logs:');
    logs.forEach(log => {
      console.log(log.name);
    });
  }
  listLogs();
  // [END logging_list_logs]
}

It does leave a hanging promise, but at least this way the sample is copy/pastable.