rpc: Use external soroban-simulation library for preflight computatio… #2

Job	Run time
Unit tests (ubuntu-20.04, 1.21)	6m 1s
Integration tests (ubuntu-20.04, 1.21, .CLI.)	15m 15s
Build (ubuntu-latest, x86_64-unknown-linux-gnu, amd64)	2m 14s
Unit tests (ubuntu-22.04, 1.21)	6m 5s
Integration tests (ubuntu-20.04, 1.21, ^Test(([^C])\|(C[^L])\|(CL[^I])).*$)	13m 44s
Build (ubuntu-latest, aarch64-unknown-linux-gnu, arm64)	2m 46s
Integration tests (ubuntu-22.04, 1.21, .CLI.)	15m 47s
Build (macos-latest, x86_64-apple-darwin, amd64)	4m 56s
Integration tests (ubuntu-22.04, 1.21, ^Test(([^C])\|(C[^L])\|(CL[^I])).*$)	13m 10s
Build (macos-latest, aarch64-apple-darwin, arm64)	5m 39s
Build (windows-latest, x86_64-pc-windows-gnu, amd64)	7m 48s
	1h 33m 25s

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