Merge #13289

13289: programgen(go): Handle conflicting names in imported packages r=abhinav a=abhinav

This fixes how programgen generates import statements
to handle conflicting imports when two imported packages
have the same name, e.g.

    github.com/pulumi/pulumi-aws/sdk/v5/go/aws/ecs
    github.com/pulumi/pulumi-awsx/sdk/go/awsx/ecs

To do this, we add a fileImporter type that tracks these imports.
It prefers unnamed imports for packages unless one of the following is
true:

- the name of the package has already been used by another import
- the name of the package does not match the last component
  of the import path (e.g., `example.com/foo-go` with `package foo`).

If the name has already been used by another import,
it attempts the following in-order:

- Combine the last two path components of the import path
  into an identifier and use that if available.
  e.g., `awsxs3` from `sdk/go/awsx/s3`.
- Append a number to the package name and increment it
  until an unused name is found.
  e.g. `ecs2`, `ecs3`, and so on.

There's a change in how this information is tracked as well.
Previously, this was a pull approach: various calls returned
programImports objects which all got merged together.

This change switches to a push approach:
as code is generated and imports are requested,
they're submitted to the fileImporter which keeps track of them
until the next `Reset()` call.
The above also has a nice side effect of dropping a parameter.

Another change worth explicitly calling out:
Previously, getModOrAlias partially duplicated some of the logic
implemented in getPulumiImport, and used `mod`, `originalMod`
in a non-obvious way.
This generated incorrect imports like the following
(note the two `/aws` at the end):

    github.com/pulumi/pulumi-aws/sdk/v5/go/aws/aws

This change replicates more of the logic of getPulumiImport
(now called addPulumiImport) into this function,
and addresses the discrepancy in codegen caused by `mod`/`originalMod`.
The result leaves most existing code unchanged,
except in a couple existing cases where the resulting changes make sense
given the logic for named imports outlined above.

Resolves #11176

Co-authored-by: Abhinav Gupta <abhinav@pulumi.com>

changelog/pending/20230626--programgen-go--fix-conflicting-imports-generated-when-two-imported-packages-have-the-same-name.yaml

@@ -0,0 +1,4 @@
+changes:
+- type: fix
+  scope: programgen/go
+  description: Fix conflicting imports generated when two imported packages have the same name.