fix: concurrent concurrent Merkle tree subtree updates #2292

Job	Run time
system-programs (account-compression, [ "cargo-test-sbf -p account-compression-test -- --test-thr...	13m 48s
system-programs (light-compressed-pda, [ "cargo-test-sbf -p compressed-pda-test -- --test-threads...	18m 55s
system-programs (light-registry, [ "cargo-test-sbf -p registry-test -- --test-threads=1" ])	17m 52s
system-programs (light-compressed-token, [ "cargo-test-sbf -p compressed-token-test -- --test-thr...	26m 24s
system-programs (token-escrow, [ "cargo-test-sbf -p token-escrow -- --test-threads=1" ])	19m 19s
system-programs (program-owned-account-test, [ "cargo-test-sbf -p program-owned-account-test -- -...	14m 25s
	1h 50m 43s

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