fix(core): applied secrets_map in load() to plain string values

[npage902]

Description: Fixes the bug in the load() function where secret placeholders in plain dicts were not replaced, even if they match a key in secrets_map, and adds a test case.

Example:

obj = {"api_key": "__SECRET_API_KEY__"}
secret_key = "secret_key_1234"
secrets_map = {"__SECRET_API_KEY__": secret_key}
result = load(obj, secrets_map=secrets_map)

Before this change, printing api_key in result would output "__SECRET_API_KEY__". Now, it will properly output "secret_key_1234".

Issue: Fixes #31804

Dependencies: None

make format, make lint, and make test have all passed on my machine.

[codspeed-hq]

CodSpeed Performance Report

Merging #33618 will improve performances by 12.5%

_{Comparing npage902:npage902/fix-load-secrets-map (2ea2e99) with master (e731ba1)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

⚡ 2 improvements
✅ 11 untouched
⏩ 21 skipped¹

Benchmarks breakdown

	Mode	Benchmark	BASE	HEAD	Change
⚡	WallTime	test_import_time[InMemoryRateLimiter]	198.4 ms	176.4 ms	+12.5%
⚡	WallTime	test_import_time[LangChainTracer]	482.6 ms	435.7 ms	+10.77%

Footnotes

1. 21 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[npage902]

Things seem to be scuffed on my end in regards to makefile testing. I'll need to look into this, but I'll just close this up for now. Apologies for any inconvenience.