Fix Issues 9999 & 10560 - [DIP1015] Deprecate & Remove implicit integer & character conversion to bool

[JinShil]

Revival of #6404

This is pending approval of this DIP: https://github.com/dlang/DIPs/blob/master/DIPs/DIP1015.md

[dlang-bot]

Thanks for your pull request, @JinShil!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	9999	enhancement	Integer literal 0 and 1 should prefer integer type in overload resolution
✓	10560	critical	Enum typed as int with value equal to 0 or 1 prefer bool over int overload

⚠️⚠️⚠️ Warnings ⚠️⚠️⚠️

• Regression or critical bug fixes should always target the stable branch. Learn more about rebasing to stable or the D release process.

To target stable perform these two steps:

1. Rebase your branch to upstream/stable:

git rebase --onto upstream/stable upstream/master

2. Change the base branch of your PR to stable

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + dmd#7310"

[wilzbach]

FYI this definitely needs to be a deprecation - building druntime already fails:

src/core/thread.d(4223): Error: cannot implicitly convert expression `0` of type `int` to `bool`
src/core/thread.d(4223): Error: cannot implicitly convert expression `0` of type `int` to `bool`

[wilzbach]

@JinShil if you change the PR back to a deprecation, Jenkins should run through all projects. You can go to "Classic" (the door button on the right) and select "Console output". It's the entire output which you can use to grep for the deprecation message. This is probably the easiest way to assess the impact of this change.

Oh and Phobos won't build with deprecation warnings.

[JinShil]

I've been informed that DIP1015 was rejected, so I'm closing this.

I urge @WalterBright and @andralex to either close issues 9999 and 10560 as invalid or offer an alternate solution.

cc @mdparker