Support wasm based plugin system

[goccy]

Example is here https://github.com/mercari/grpc-federation/tree/wasm/_examples/15_plugin

The plugin feature is available to extend CEL APIs.
For example, this sample adds a library using Go's regular expressions to the example.regexp package .

[github-actions]

Code Metrics Report

	main (203b2fe)	#91 (a0cf46f)	+/-
Coverage	64.4%	60.7%	-3.7%
Code to Test Ratio	1:0.5	1:0.4	-0.0
Test Execution Time	3m33s	3m42s	+9s

Details

  |                     | main (203b2fe) | #91 (a0cf46f) |  +/-  |
  |---------------------|----------------|---------------|-------|
- | Coverage            |          64.4% |         60.7% | -3.7% |
  |   Files             |             62 |            66 |    +4 |
  |   Lines             |           8848 |          9422 |  +574 |
+ |   Covered           |           5700 |          5722 |   +22 |
- | Code to Test Ratio  |          1:0.5 |         1:0.4 |  -0.0 |
  |   Code              |          24692 |         25825 | +1133 |
+ |   Test              |          11255 |         11366 |  +111 |
- | Test Execution Time |          3m33s |         3m42s |   +9s |

Code coverage of files in pull request scope (77.0% → 65.4%)

Files	Coverage	+/-
generator/code_generator.go	81.2%	-5.0%
grpc/federation/cel.go	0.0%	0.0%
grpc/federation/cel/plugin.go	0.0%	0.0%
grpc/federation/cel/wasm.go	0.0%	0.0%
grpc/federation/context.go	0.0%	0.0%
grpc/federation/error.go	0.0%	0.0%
grpc/federation/lib.go	0.0%	0.0%
grpc/federation/otel.go	0.0%	0.0%
grpc/federation/plugin.pb.go	4.1%	+4.1%
grpc/federation/plugin_host.go	0.0%	0.0%
grpc/federation/validation.go	0.0%	0.0%
internal/testutil/cmpopt.go	100.0%	0.0%
resolver/cel.go	59.0%	-21.0%
resolver/context.go	70.9%	-20.9%
resolver/resolver.go	83.9%	-4.1%
resolver/types.go	90.5%	0.0%
source/location.go	55.6%	-4.1%
types/types.go	7.9%	-7.1%

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Reported by octocov