module/apmsql: parse SQL

[axw]

• PostgreSQL $tag$ quotes
• Handle db.schema.table (we currently handle schema.table and table)
• more tests (see https://github.com/elastic/apm-agent-python/blob/master/tests/instrumentation/psycopg2_tests.py for a good assortment)

Closes #103

[codecov-io]

Codecov Report

Merging #129 into master will increase coverage by 0.78%.
The diff coverage is 87.14%.

@@            Coverage Diff             @@
##           master     #129      +/-   ##
==========================================
+ Coverage   75.99%   76.78%   +0.78%     
==========================================
  Files          61       64       +3     
  Lines        3558     3834     +276     
==========================================
+ Hits         2704     2944     +240     
- Misses        659      681      +22     
- Partials      195      209      +14

Impacted Files	Coverage Δ
module/apmsql/driver.go	66.66% <100%> (+1.96%)	⬆️
module/apmsql/internal/sqlscanner/token.go	60% <60%> (ø)
module/apmsql/signature.go	84.7% <84.7%> (ø)
module/apmsql/internal/sqlscanner/scanner.go	88.88% <88.88%> (ø)
tracer.go	84.34% <0%> (-0.58%)	⬇️

---

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 7c25a1a...8c8e283. Read the comment docs.

[axw]

Added some more tests based on those in apm-agent-python. Also added a simple fuzz test, and benchmark.