soroban-rpc: Allow Budget Instruction Leeway to be Configured by Clients #3104

Job	Run time
Build (ubuntu-latest, x86_64-unknown-linux-gnu, amd64)	2m 32s
Integration tests (ubuntu-20.04, 1.21, .CLI.)	14m 38s
Build (ubuntu-latest, aarch64-unknown-linux-gnu, arm64)	2m 38s
Integration tests (ubuntu-20.04, 1.21, ^Test(([^C])\|(C[^L])\|(CL[^I])).*$)	12m 33s
Build (macos-latest, x86_64-apple-darwin, amd64)	4m 3s
Build (macos-latest, aarch64-apple-darwin, arm64)	4m 34s
Build (windows-latest, x86_64-pc-windows-gnu, amd64)	7m 27s
Unit tests (ubuntu-20.04, 1.21)	5m 15s
	53m 40s

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