tidy: clean up code for env loader

[paperdave]

What does this PR do?

Fixes #9635
Fixes #9445
Supercedes #9448

When we moved from std.process to our own spawn implementation, we moved from stdEnvMap to createNullDelimitedEnvMap in many places. i would like to highlight one line of the former:

        while (iter.next()) |entry| {
+           // Allow var from .env.development or .env.production to be loaded again
+           if (!entry.value_ptr.conditional) {
                try env_map.hash_map.put(entry.key_ptr.*, entry.value_ptr.value);
            }
        }

Such check is not present in createNullDelimitedEnvMap. We started passing a bunch of .conditional = true variables to subprocesses.

This PR removes .conditional and changes HashTableValue into just string. then, instead of loading variables that never get passed to subprocess, let's just not load them. the code reads much nicer.

After adding this check, it works, however this .conditional = true flag does not make any sense to me. I detail some more about this issue in this comment which is worth reading to get an understanding of the broken behavior this fixes.

As for createNullDelimitedEnvMap, when i made the change, i also turned the entire operation into a single allocation, instead of many smaller ones. This will make the memory easier to free (it is still a memory leak... maybe i fix)

---

I verify this code works by having many new tests, all of which i verify work on Bun 1.0.33, a commit before the regression.

[github-actions]

❌ @paperdave 2 files with test failures on linux-x64-baseline:

• test/integration/next/default-pages-dir/test/next-build.test.ts SIGTERM
• test/js/node/http2/node-http2.test.js SIGSEGV

View test output

^{#4da56acd51d23e2d282b581fdccb1ac993dfd067}

[github-actions]

❌ @paperdave 3 files with test failures on linux-x64:

• test/integration/mysql2/mysql2.test.ts 6 failing
• test/integration/next/default-pages-dir/test/next-build.test.ts SIGTERM
• test/js/node/http2/node-http2.test.js SIGSEGV

View test output

^{#4da56acd51d23e2d282b581fdccb1ac993dfd067}

[github-actions]

❌🪟 @paperdave, there are 10 test regressions on Windows x86_64

• test\cli\install\bun-run-bunfig.test.ts
• test\cli\install\bunx.test.ts
• test\cli\run\env.test.ts
• test\cli\test\bun-test.test.ts
• test\cli\install\registry\bun-install-registry.test.ts
• test\js\bun\console\console-iterator.test.ts
• test\js\node\dns\node-dns.test.js
• test\js\node\stream\node-stream.test.js
• test\js\web\fetch\body-stream.test.ts
• test\js\third_party\postgres\postgres.test.ts

Full Test Output

[github-actions]

❌ @paperdave 7 files with test failures on bun-darwin-aarch64:

• test/integration/next/default-pages-dir/test/next-build.test.ts SIGTERM
• test/js/bun/http/serve.test.ts 10 failing
• test/js/bun/shell/leak.test.ts SIGTERM
• test/js/bun/test/test-test.test.ts 1 failing
• test/js/third_party/prisma/prisma.test.ts SIGABRT
• test/js/third_party/prompts/prompts.test.ts 1 failing
• test/js/web/timers/setTimeout.test.js 1 failing

View test output

^{#4da56acd51d23e2d282b581fdccb1ac993dfd067}

[github-actions]

❌ @paperdave 5 files with test failures on bun-darwin-x64:

• test/cli/install/registry/bun-install-registry.test.ts 10 failing
• test/integration/next/default-pages-dir/test/next-build.test.ts SIGTERM
• test/js/bun/shell/leak.test.ts 1 failing
• test/js/third_party/prisma/prisma.test.ts 2 failing
• test/regression/issue/02499.test.ts SIGTERM

View test output

^{#4da56acd51d23e2d282b581fdccb1ac993dfd067}

[Jarred-Sumner]

Nice

[dylan-conway]

nice

[jdalton]

@paperdave I'm glad you caught this. I'm wary of our policy of recreating the wheel of APIs that exist in the platform in part because of things like this that fall through the cracks. I'd rather contribute to fixing the lower level APIs where possible and deviating from them only when reaaally needed.