refactor: Remove batch concept from opendal

[Xuanwo]

Which issue does this PR close?

Part of #3922

Rationale for this change

Batch doesn't exist in opendal anymore.

What changes are included in this PR?

Remove batch capability.

Are there any user-facing changes?

batch capability has been removed.

[codspeed-hq]

CodSpeed Performance Report

Merging #5393 will degrade performances by 15.89%

_{Comparing remove-batch (dc5fb7c) with main (c77a07a)}

Summary

⚡ 5 improvements
❌ 4 regressions
✅ 64 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	remove-batch	Change
⚡	buffer 256 KiB * 32 advance	660.6 ns	573.1 ns	+15.27%
⚡	buffer 256 KiB * 4 advance	660.6 ns	573.1 ns	+15.27%
⚡	buffer 4.00 MiB * 32 advance	660.6 ns	573.1 ns	+15.27%
⚡	buffer 4.00 MiB * 4 advance	660.6 ns	573.1 ns	+15.27%
❌	256 KiB * 1000k chunk	154.4 ns	183.6 ns	-15.89%
❌	256 KiB * 100k chunk	154.4 ns	183.6 ns	-15.89%
❌	256 KiB * 10k chunk	154.4 ns	183.6 ns	-15.89%
❌	256 KiB * 1k chunk	183.6 ns	212.8 ns	-13.71%
⚡	concurrent 4	411.7 µs	365.5 µs	+12.63%

[Xuanwo]

Thank you @WenyXu for the review!