perf(db-mongodb): improve performance of all operations, up to 50% faster

[r1tsuu]

This PR improves speed and memory efficiency across all operations with the Mongoose adapter.

How?

• Removes Mongoose layer from all database calls, instead uses MongoDB directly.
• Replaces deep copying of read results using JSON.parse(JSON.stringify(data)) with the transform operation: 'read' function which converts Date's, ObjectID's in relationships / joins to strings. As before, it also handles transformations for write operations.
• Faster hasNearConstraint for potentially large where's
• traverseFields now can accept flattenedFields which we use in transform. Less recursive calls with tabs/rows/collapsible

Additional fixes

• Uses current transaction for querying nested relationships properties in buildQuery, previously it wasn't used which could've led to wrong results
• Allows to clear not required point fields with passing null from the Local API. Previously it didn't work in both, MongoDB and Postgres

Benchmarks using this file https://github.com/payloadcms/payload/blob/chore/db-benchmark/test/_community/int.spec.ts

Small Dataset Performance

Metric	Before Optimization	After Optimization	Improvement (%)
Average FULL (ms)	1170	844	27.86%
payload.db.create (ms)	1413	691	51.12%
payload.db.find (ms)	2856	2204	22.83%
payload.db.deleteMany (ms)	15206	8439	44.53%
payload.db.updateOne (ms)	21444	12162	43.30%
payload.db.findOne (ms)	159	112	29.56%
payload.db.deleteOne (ms)	3729	2578	30.89%
DB small FULL (ms)	64473	46451	27.93%

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Medium Dataset Performance

Metric	Before Optimization	After Optimization	Improvement (%)
Average FULL (ms)	9407	6210	33.99%
payload.db.create (ms)	10270	4321	57.93%
payload.db.find (ms)	20814	16036	22.93%
payload.db.deleteMany (ms)	126351	61789	51.11%
payload.db.updateOne (ms)	201782	99943	50.49%
payload.db.findOne (ms)	1081	817	24.43%
payload.db.deleteOne (ms)	28534	23363	18.12%
DB medium FULL (ms)	519518	342194	34.13%

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Large Dataset Performance

Metric	Before Optimization	After Optimization	Improvement (%)
Average FULL (ms)	26575	17509	34.14%
payload.db.create (ms)	29085	12196	58.08%
payload.db.find (ms)	58497	43838	25.04%
payload.db.deleteMany (ms)	372195	173218	53.47%
payload.db.updateOne (ms)	544089	288350	47.00%
payload.db.findOne (ms)	3058	2197	28.14%
payload.db.deleteOne (ms)	82444	64730	21.49%
DB large FULL (ms)	1461097	969714	33.62%