fix: support pg tracing in dd-trace-js

[mattkrick]

Description

dd-trace-js only works by monkeypatching the require statement. https://docs.datadoghq.com/tracing/trace_collection/automatic_instrumentation/dd_libraries/nodejs/#bundling
No shade to the authors, but it's really hacky & there's no workaround.

That means if we want tracing for PG, we need a native require statement in our webpack bundle.
We could exclude pg from the bundle, but that means we'd have to ship the entirety of node_modules, adding gigabytes to our docker image.
We have to include all of node_modules because pg has dependencies that must also be included. And those dependencies have dependencies, and it's turtles all the way down.

The solution in this PR bundles pg and all its dependencies into a single file and outputs it to /dist/node_modules/pg/lib/index.js, alongside pg's package.json. In doing so, we're tricking dd-trace-js into thinking that our custom pg entrypoint is actually a node module. The result is an extra entrypoint, but no increase in this size of the output. In development, require('pg') resolves to ./pg.ts, so there is no change.

Since we use require('pg'), pg.ts must exist in the same directory. Since pg.d.ts already existed in that directory, I had to move it to ./types since pg.ts has nothing to do with pg.d.ts

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This PR exceeds the recommended size of 1000 lines. Please make sure you are NOT addressing multiple issues with one PR. Note this PR will be delayed and might be rejected due to its size.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Please make sure you are NOT addressing multiple issues with one PR. Note this PR will be delayed and might be rejected due to its size.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Please make sure you are NOT addressing multiple issues with one PR. Note this PR will be delayed and might be rejected due to its size.

[github-actions]

This PR exceeds the recommended size of 1000 lines. Please make sure you are NOT addressing multiple issues with one PR. Note this PR will be delayed and might be rejected due to its size.