Add enum selector

[goccy]

• Treats enum identifier as opaque<int> type at compile time
• Refactor generator templates to add the enum selector process
• Add grpc.federation.enum.select function to select different enum values for using field binding by multiple aliases

[github-actions[bot]]

Code Metrics Report

	main (fad997c)	#200 (aafe992)	+/-
Coverage	65.3%	65.1%	-0.2%
Code to Test Ratio	1:0.3	1:0.3	-0.0
Test Execution Time	7m4s	7m5s	+1s

Details

``` diff | | main (fad997c) | #200 (aafe992) | +/- | |---------------------|----------------|----------------|-------| - | Coverage | 65.3% | 65.1% | -0.2% | | Files | 68 | 69 | +1 | | Lines | 11274 | 11415 | +141 | + | Covered | 7366 | 7431 | +65 | - | Code to Test Ratio | 1:0.3 | 1:0.3 | -0.0 | | Code | 35854 | 36209 | +355 | + | Test | 12509 | 12517 | +8 | - | Test Execution Time | 7m4s | 7m5s | +1s | ```

Code coverage of files in pull request scope (81.5% → 80.1%)

Files	Coverage	+/-
generator/code_generator.go	79.6%	-0.9%
grpc/federation/cel/enum.go	54.8%	+54.8%
grpc/federation/cel/lib.go	88.0%	0.0%
resolver/cel.go	75.5%	-1.0%
resolver/fqdn.go	100.0%	+11.5%
resolver/message.go	75.3%	-0.2%
resolver/resolver.go	82.1%	-0.8%
resolver/type_conversion.go	84.1%	-10.0%

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Reported by octocov