Generics are not supported by analyzers

[chressie]

Bug report

Describe the bug
Generics are not supported by analyzers or helper functions. Most notably the new *types.TypeParam type is not recognized.

To Reproduce

1. Upgrade x/tools to a recent version (which supports ssa + generics):

go get golang.org/x/tools@v0.1.11-0.20220504225841-45c8a7131235
go mod download github.com/yuin/goldmark 
go get golang.org/x/tools/internal/gocommand@v0.1.11-0.20220504225841-45c8a7131235

2. Add a generic type with a method to internal/pkg/sourcetype/testdata/test_stackoverflow.go

E.g.

type G[T any]struct{}

func (G[T]) M(_ T) {
}

3. Run the sourcetype test in verbose mode:

% go test -v ./internal/pkg/sourcetype
=== RUN   TestSourceTypeDoesNotStackOverflow
unexpected type received: *types.TypeParam T; please report this issue
--- PASS: TestSourceTypeDoesNotStackOverflow (0.02s)
PASS
ok  	github.com/google/go-flow-levee/internal/pkg/sourcetype	0.048s

Note the unexpected type received: *types.TypeParam T; please report this issue in the output.

Additional context
n/a