Show "exec" todos in the list of rebase todos

PR Description

It is sometimes useful to perform a git rebase -x "make test" origin/main in order to verify that all commits of the current branch are green. However, if the rebase stops in the middle because one of those tests fail, it's easy to accidentally press m <enter> in lazygit after amending some fix, not realizing that the rest of the tests will now run invisibly inside lazygit.

This PR makes two changes to improve this situation:

It shows exec todos in the commits panel:
when continuing a rebase and there are exec todos, it suspends itself to the background so that you can see the output of the test runs in the terminal.

We can improve this further in the future; for example, it would often be useful to be able to delete some of the exec commands, this is not currently possible. But it's still better than before.

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 906d21f3cea91d5a11ce06630804aae99115a74c[^1]	:white_check_mark: 100.00%

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (906d21f3cea91d5a11ce06630804aae99115a74c) | Report Missing | Report Missing | Report Missing | | | Head commit (92dd80c3e3af0c399261272889cc21c5efaaac08) | 52054 | 45012 | 86.47% | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#3654) | 48 | 48 | **100.00%** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

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_{Codacy stopped sending the deprecated coverage status on June 5th, 2024. Learn more} [^1]: Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct.

jesseduffield / lazygit