Add feature detection properties to DbProviderFactory

[roji]

CanCreateDataAdapter, CanCreateCommandBuilder

Closes #35564

[stephentoub]

Ah, GitHub webhooks are down:
https://www.githubstatus.com/
"We deployed a fix and are processing the Webhook backlog. "

[divega]

@roji Just posted a couple of comments. Assuming you address them this looks good.

[divega]

Is this code thread safe? I cannot actually think of any race condition that matters, but bringing it up in case others can. E.g. I am not sure if Nullable<T> assignment is atomic, but I am also not sure it matters because worse case you may end up creating the adapter multiple times, and I don't think the property will return wrong results.

[roji]

Assignment of a reference is atomic, i.e. no value tearing can occur. So yes, at worst multiple data adapters may get created, but I think the code is be safe.

[roji]

Here's the spec paragraph on reference atomicity:

Reads and writes of the following data types are atomic: bool, char, byte, sbyte, short, ushort, uint, int, float, and reference types. In addition, reads and writes of enum types with an underlying type in the previous list are also atomic. Reads and writes of other types, including long, ulong, double, and decimal, as well as user-defined types, are not guaranteed to be atomic. Aside from the library functions designed for that purpose, there is no guarantee of atomic read-modify-write, such as in the case of increment or decrement.

[divega]

Idem

[roji]

Idem

[roji]

@divega merging this assuming that there's no thread-safety issues - at the very worse we'll fix later.