[release-7.4] Fix an old exclude failed bug

[spraza]

Port #13645 to release-7.4.

Problem: In removeKeysFromFailedServer, the writes that unassign a dropped shard from the dest servers (serverKeysFalse) and the writes that reassign it to the new team as an empty range were pushed into a single actors vector and awaited together. krmSetRangeCoalescing performs a read-modify-write on the serverKeys map, so when a server appears in both the dest set and the new team, running the two batches concurrently lets the coalescing reads observe stale state and produce an incorrect serverKeys assignment.

Solution: await the unassign batch first, then run the empty-range assignment in a separate batch, ensuring the serverKey map assignment is correct.

Same fix already backported to release-7.3 in #13662. release-7.4 still used the wait()/actor-compiler style rather than main's co_await, and shardId needed to become state since it now crosses the new wait() boundary -- same conflict resolution as the 7.3 backport.

100K: 20260813-171407-praza-port-7.4-pr13645-817f-e3951c728b485de6 pass=100000 fail=0 ended=100000 max_runs=100000

[foundationdb-ci]

Result of foundationdb-pr-clang-arm on Linux RHEL 9

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[foundationdb-ci]

Result of foundationdb-pr-macos-m1 on macOS 14.x

• Commit ID: 17f7513
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[foundationdb-ci]

Result of foundationdb-pr-clang on Linux RHEL 9

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[foundationdb-ci]

Result of foundationdb-pr on Linux RHEL 9

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[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux RHEL 9

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[foundationdb-ci]

Result of foundationdb-pr-macos on macOS 14.x

• Commit ID: 17f7513
• Duration 4:37:19
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