Fixes Termination Manager logging to report aggregated percentage of environments done due to each term.  (#3107)

# Description

Currently Termination Manager write current step's done count for each
term if reset is detected. This leads to two problem.
1. User sees different counts just by varying num_envs
2. the count can be over-count or under-count depending on when reset
happens, as pointed out in #2977 (Thanks, @Kyu3224)

The cause of the bug is because we are reporting current step status
into a buffer that suppose to record episodic done. So instead of write
the entire buffer base on current value, we ask the update to respect
the non-reseting environment's old value, and instead of reporting
count, we report percentage of environment that was done due to the
particular term.

Test on Isaac-Velocity-Rough-Anymal-C-v0

Before fix:
<img width="786" height="323" alt="Screenshot from 2025-08-06 22-16-20"
src="https://github.com/user-attachments/assets/4838d612-7f0e-4232-a07e-688b547e91db"
/>
Red: num_envs = 4096, Orange: num_envs = 1024

After fix:

<img width="786" height="323" alt="Screenshot from 2025-08-06 22-16-12"
src="https://github.com/user-attachments/assets/e6e55c21-17ed-42ca-8d94-a19d08611f86"
/>
Red: num_envs = 4096, Orange: num_envs = 1024

Note that curve of the same color ran on same seed, and curves matched
exactly, the only difference is the data gets reported in termination.
The percentage version is a lot more clear in conveying how agent
currently fails, and how much percentage of agent fails, and shows that
increasing num_envs to 4096 helps improve agent avoiding termination by
`base_contact` much quicker than num_envs=1024. Such message is a bit
hard to tell in first image.

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## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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