Fix index method name collisions

[theunrepentantgeek]

What this PR does / why we need it:

We are now encountering collisions with our generated index method names, caused by having multiple properties nested (via different paths) with the same name.

This PR uses parts of the full property path to the property to avoid collisions, as we discussed offline.

Closes #2332

Special notes for your reviewer:

Takes the preexisting indexFunctionBuilderContext type and converts it into a full abstraction for a property chain. The implementation is changed so that chains form a tree of (nearly) immutable references, both to keep memory use down and to allow disambiguation.

How does this PR make you feel:

If applicable:

• this PR contains tests

[codecov-commenter]

Codecov Report

Merging #2335 (a158fa5) into main (9603436) will increase coverage by 0.00%.
The diff coverage is 64.17%.

❗ Current head a158fa5 differs from pull request most recent head cbe6226. Consider uploading reports for the commit cbe6226 to get more accurate results

@@           Coverage Diff           @@
##             main    #2335   +/-   ##
=======================================
  Coverage   53.21%   53.21%           
=======================================
  Files         853      853           
  Lines      259188   259246   +58     
=======================================
+ Hits       137930   137964   +34     
- Misses     101869   101887   +18     
- Partials    19389    19395    +6     

Impacted Files	Coverage Δ
...n/pipeline/export_controller_type_registrations.go	36.49% <64.17%> (+28.88%)	⬆️
...ernal/testcommon/error_translating_roundtripper.go	11.53% <0.00%> (-50.00%)	⬇️
v2/internal/metrics/arm_client_metrics.go	84.00% <0.00%> (-8.00%)	⬇️
v2/internal/genericarmclient/generic_client.go	77.35% <0.00%> (-1.89%)	⬇️
...ilers/arm/azure_generic_arm_reconciler_instance.go	73.73% <0.00%> (-0.60%)	⬇️
v2/internal/testcommon/kube_per_test_context.go	87.28% <0.00%> (+0.05%)	⬆️
...rmysql/v1beta20210501/flexible_server_types_gen.go	60.16% <0.00%> (+0.74%)	⬆️
v2/internal/reconcilers/common.go	82.75% <0.00%> (+2.75%)	⬆️

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[matthchr]

I've also made changes here to resolve the issue raised by @majguo in #2330, and I suspect our changes are going to conflict. Let's sync up and determine what order to merge them in @theunrepentantgeek.