wallet2: adjust fee during backlog, fix set priority

[selsta]

Resolves #9221

The automatic fee level should switch between slow and normal depending on the current backlog.

https://monero.stackexchange.com/questions/11657/what-are-the-standard-fee-multiplier-levels#comment10765_11658

This behaviour broke at some point, likely during the 2021 fee code changes. This PR restores the previous behaviour.

[jeffro256]

I don't think that I agree with these changes. Sometimes, one knows that there's a backlog, but trusts that their transaction will make it into the block in an acceptable timeframe. Forcing the priority to rise because of a backlog gives attackers more leverage to disrupt the network.

[SamsungGalaxyPlayer]

The intent of the automatic feature has always been to alternate between the slow and normal fee levels as appropriate. I recommend that unless there's a really strong reason to completely change the logic behind these fee level adjustments, the discrepancy versus the expected behavior is addressed.

[selsta]

@jeffro256 the current code is broken since the 2021 fee changes. This PR fixes that back to the previous behavior.

Also in your example couldn't you manually select the lowest fee instead of auto?

[LocalMonero]

This returns the expected behavior. The mempool spam would be much less noticeable by common users had this bug not been introduced in 2021. Thanks @selsta for fixing it so quickly, and @luigi1111 please merge this urgently and release the new binaries for everyone.

[selsta]

Should I also change the remaining return priority; to either 1 or 2?

[nahuhh]

LGTM

anonero wallet's @r4v3r23 pulled pr and tested on anonero.

[r4v3r23]

standard tx fees are now ~4x the size than previous code's behavior

+1 from me

[osensei]

So, I've done some tests with these changes, and it seems to work as expected ONLY when wallet's settings are:
priority = 0 AND auto-low-priority = 1

In any other case the priority setting seems to be ignored, and will always send with the minimum fee, even if you set priority = 4 AND auto-low-priority = 0. This also happens on v0.18.3.1.

In those other cases, the only way to override the minimum fee is to specify the priority in the transfer command, .e.g.:
transfer normal <address> <amount>

[osensei]

In any other case the priority setting seems to be ignored, and will always send with the minimum fee, even if you set priority = 4 AND auto-low-priority = 0. This also happens on v0.18.3.1.

I understand that my observations may not apply directly to this PR, but just wanted to state the facts, as it seemed relevant. Also, I just saw that @selsta opened #9221 related to this.

[SChernykh]

In any other case the priority setting seems to be ignored, and will always send with the minimum fee, even if you set priority = 4 AND auto-low-priority = 0. This also happens on v0.18.3.1.

See my comment there. #9219 should fix it too.

Edit: uhh, I was probably wrong and #9221 will probably require a separate fix.