perf: avoid AST depth depending on pnpm workspace size (#2865)

This converts 2 `if/elif bazel_package == "pnpm-project-path"` blocks
into 2 constants and the `if/elif` is replaced with a lookup into the
constant. See the diffs of the snapshot files for the best outline of
the changes.

This prevents a reported `java.lang.StackOverflowError` from the bazel
starlark parser treating `elif` as nested `else: if`. This reduces the
`npm_link_all_packages()` from N `if/elif` statements into a single map
lookup. The tradeoff is when the generated `defs.bzl` is `load()`ed it
now has 2 giant maps declared at load time.

Overall I (and my robot assistants, and my testing on a repo with ~2k
pnpm workspace projects) think this has negligible impact on actually
performance but should avoid the `java.lang.StackOverflowError`.

### Changes are visible to end-users: no

### Test plan

- Covered by existing test cases

Author: jbedard

.aspect/config.axl

@@ -44,6 +44,9 @@ buildifier = format.alias(
             "**/*.bzl",
             "**/*.star",
         ],
+        "exclude_patterns": [
+            "**/snapshots/**",
+        ],
     },
     summary = "Format Starlark files using buildifier.",
 )