Fix the bug that operation_name table can not be init more than once

[guo0693]

Signed-off-by: Jun Guo guo0693@gmail.com

Which problem is this PR solving?

• If we materialize the operation_names schema more than once, the original query template will be changed to something like
  INSERT INTO operation_names_v2(service_name, span_kind, operation_name) VALUES (?, ?, ?)%!!(string=operation_names_v2)(EXTRA string=operation_names_v2)

Short description of the changes

• Do not use pointer for schemas map. Always materialize the copied struct for the storage use

[codecov]

Codecov Report

Merging #1961 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1961      +/-   ##
==========================================
- Coverage   98.48%   98.46%   -0.03%     
==========================================
  Files         199      199              
  Lines        9875     9875              
==========================================
- Hits         9725     9723       -2     
- Misses        115      116       +1     
- Partials       35       36       +1

Impacted Files	Coverage Δ
...gin/storage/cassandra/spanstore/operation_names.go	97.59% <ø> (ø)	⬆️
cmd/query/app/static_handler.go	86.84% <0%> (-1.76%)	⬇️

---

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 e4b97b3...631f7b4. Read the comment docs.