esbuild output with `preserveSymlinks = false` contains machine-specific relative paths

Originally reported in https://github.com/aspect-build/rules_esbuild/pull/32#issuecomment-1193356744:

> Another problem with `preserveSymlinks = false` for our needs in Bazel is that ESBuild leaves comments in the output that contain resolved file paths. With `preserveSymlinks = false` these can refer to paths like `.../home/matt/.cache/bazel_matt/.../.../...` which, across different users and checkouts, will generate downstream cache misses on actions that depend on the outputs.

At Figma we encountered this issue with a `write_source_files` target that writes an esbuild bundle. The associated `diff_test` fails with rules_esbuild 0.12+ because the generated relative path differs between local development and CI.

Start by reviewing the preserveSymlinks handling and the linked pull-request discussion, then reproduce the failure with the mentioned write_source_files target and diff_test. Done means esbuild output no longer embeds machine-specific relative paths, so the generated diff is identical across local development and CI.

Written by the indexing model from the issue text.