loadPackage fails for hard to determine reason

Nobody has claimed this yet.

Sometimes, calling `loadPackage` can fail, saying it cannot be reloaded.

This error occurred in a set of packages I wrote a few years ago. I have boiled it down to its essence:

In `A.m2`, place the code
```
newPackage("A", Headline => "A")

```

In `B.m2`, place the code
```
needsPackage "A"
newPackage("B", Headline => "B")
```

Now after creating these files, try the following code.
```
elapsedTime installPackage "A"
elapsedTime installPackage "B"
restart
loadPackage "A"
```

This last line fails, since the package ''A" has been loaded when "B" is being scanned for its newPackage code (I think), and so has already been loaded. This is very hard to determine, as any installed package could do this and cause the package to simply be loaded already... Using `needsPackage` works fine.

Also, the time to install the package "A" seems to take 4-5 seconds on my machine, which seems quite large. (Same with "B").

Reproduce the failure with the A.m2 and B.m2 examples, then run the listed installPackage, restart, loadPackage, and needsPackage commands. Trace the package-loading path used by these commands and determine why A is considered already loaded; also measure whether the reported 4–5 second installation time is part of the same issue. Done means the reload behavior and installation-time concern have a clear resolution or documented scope.

Written by the indexing model from the issue text.