feat: revert changes to `ValueMerger` and `Instruction::IfElse` #16051

Job	Run time
build-noirc-abi	1m 29s
build-acvm-js	1m 27s
build-nargo	2m 30s
build-noir-wasm	4m 11s
ACVM JS (Browser)	1m 19s
ACVM JS (Node.js)	39s
noirc_abi	1m 45s
Example scripts	29s
noir_codegen	1m 9s
Noir JS	1m 17s
Check external repo - noir-lang/ec	36s
Check external repo - noir-lang/eddsa	11s
Check external repo - noir-lang/mimc	6s
Check external repo - noir-lang/noir_sort	6s
Check external repo - noir-lang/noir-edwards	14s
Check external repo - noir-lang/noir-bignum	34s
Check external repo - noir-lang/noir_bigcurve	3m 42s
Check external repo - noir-lang/noir_base64	12s
Check external repo - noir-lang/noir_string_search	6s
Check external repo - noir-lang/sparse_array	15s
Check external repo - noir-lang/noir_rsa	10s
Check external repo - AztecProtocol/aztec-packages	30s
Check external repo - AztecProtocol/aztec-packages	49s
Check external repo - AztecProtocol/aztec-packages	30s
Check external repo - AztecProtocol/aztec-packages	3m 40s
Check external repo - AztecProtocol/aztec-packages	18s
Check external repo - AztecProtocol/aztec-packages	32m 51s
Check external repo - AztecProtocol/aztec-packages	1m 22s
Integration Tests (Browser)	2m 35s
Integration Tests (Node)	2m 24s
noir_wasm	1m 31s
End	1s
	1h 8m 58s

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