soroban-rpc: Allow Budget Instruction Leeway to be Configured by Clients #3106

Job	Run time
Unit tests (ubuntu-20.04, 1.21)	5m 24s
Integration tests (ubuntu-20.04, 1.21, .CLI.)	14m 18s
Build (ubuntu-latest, x86_64-unknown-linux-gnu, amd64)	2m 14s
Integration tests (ubuntu-20.04, 1.21, ^Test(([^C])\|(C[^L])\|(CL[^I])).*$)	12m 42s
Build (ubuntu-latest, aarch64-unknown-linux-gnu, arm64)	2m 46s
Build (macos-latest, x86_64-apple-darwin, amd64)	4m 19s
Build (macos-latest, aarch64-apple-darwin, arm64)	4m 58s
Build (windows-latest, x86_64-pc-windows-gnu, amd64)	7m 9s
	53m 50s

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