add schema definition deep copying and mechanism to inspect or alter schema definitions before compilation

[ccbrown]

This PR adds a Clone method to the schema definition types.

This also adds a mechanism to inspect and alter the schema definition before it's built.

What it Does

Steps to Test

go test -v ./...

[codecov]

Codecov Report

Merging #58 (5cf3ae8) into main (0ebcee0) will decrease coverage by 1.21%.
The diff coverage is 49.21%.

@@            Coverage Diff             @@
##             main      #58      +/-   ##
==========================================
- Coverage   81.19%   79.99%   -1.21%     
==========================================
  Files          55       56       +1     
  Lines        4376     4558     +182     
==========================================
+ Hits         3553     3646      +93     
- Misses        537      611      +74     
- Partials      286      301      +15     

Impacted Files	Coverage Δ
graphql/schema/inspect.go	84.21% <33.33%> (+4.72%)	⬆️
config.go	80.00% <40.00%> (-4.79%)	⬇️
graphql/schema/deep_copy.go	50.00% <50.00%> (ø)
graphql/schema/schema.go	77.65% <100.00%> (+0.24%)	⬆️

... and 1 file with indirect coverage changes