Fix bug with R/O transaction destroyed before futures, add GC references for db/tx

In a previous PR the R/O transaction was optimized and the finalizer was removed; however this prevents using any future, since transaction is already destroyed by the time future is attempted evaluation.

Additionally, a new issue is uncovered and addressed: the Go Database, Transaction and Future objects are all garbage-collected independently, which is incorrect because Database and Transaction must not be garbage-collected if any future has not yet been garbage-collected.

A test has been added to verify that futures work right after their creation within a ReadTransact call.

Code-Reviewer Section

[x] The PR has a description, explaining both the problem and the solution.
[x] The description mentions which forms of testing were done and the testing seems reasonable.
[x] Every function/class/actor that was touched is reasonably well documented.

For Release-Branches

If this PR is made against a release-branch, please also check the following:

[ ] This change/bugfix is a cherry-pick from the next younger branch (younger release-branch or main if this is the youngest branch)
[ ] There is a good reason why this PR needs to go into a release branch and this reason is documented (either in the description above or in a linked GitHub issue)

Aug 27 '24 14:08 gm42

Cc @johscheuer

Aug 27 '24 14:08 gm42

Result of foundationdb-pr-macos-m1 on macOS Ventura 13.x

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 0:07:15
Result: :x: FAILED
Error: Error while executing command: ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ${HOME}/.ssh_key ec2-user@${MAC_EC2_HOST} /opt/homebrew/bin/bash --login -c ./build_pr_macos.sh. Reason: exit status 1
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Build Workspace zip file of the working directory (available for 30 days)

Aug 27 '24 18:08 foundationdb-ci

Result of foundationdb-pr-macos on macOS Ventura 13.x

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 0:11:52
Result: :x: FAILED
Error: Error while executing command: ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ${HOME}/.ssh_key ec2-user@${MAC_EC2_HOST} /usr/local/bin/bash --login -c ./build_pr_macos.sh. Reason: exit status 1
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Build Workspace zip file of the working directory (available for 30 days)

Aug 27 '24 18:08 foundationdb-ci

Result of foundationdb-pr-clang-ide on Linux CentOS 7

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 0:20:31
Result: :white_check_mark: SUCCEEDED
Error: N/A
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Build Workspace zip file of the working directory (available for 30 days)

Aug 27 '24 18:08 foundationdb-ci

Result of foundationdb-pr on Linux CentOS 7

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 0:41:13
Result: :x: FAILED
Error: Error while executing command: ctest -j ${NPROC} --no-compress-output -T test --output-on-failure. Reason: exit status 8
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Aug 27 '24 19:08 foundationdb-ci

Result of foundationdb-pr-clang-arm on Linux CentOS 7

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 0:51:14
Result: :white_check_mark: SUCCEEDED
Error: N/A
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Aug 27 '24 19:08 foundationdb-ci

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 0:56:41
Result: :white_check_mark: SUCCEEDED
Error: N/A
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Build Workspace zip file of the working directory (available for 30 days)
Cluster Test Logs zip file of the test logs (available for 30 days)

Aug 27 '24 19:08 foundationdb-ci

Result of foundationdb-pr-clang on Linux CentOS 7

Commit ID: 1780932466b56388fad0d24e8e9adb07ee827129
Duration 1:22:05
Result: :white_check_mark: SUCCEEDED
Error: N/A
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Build Workspace zip file of the working directory (available for 30 days)

Aug 27 '24 20:08 foundationdb-ci

It looks like I cannot see the reason for the failures :thinking:

Edit: found the logs, they look like errors in compiling fdbmonitor

Aug 28 '24 06:08 gm42