Improve file handling on Windows

[sake92]

Changes:

• replace new FileInputStream with Files.newInputStream
• replace new FileOutputStream with Files.newOutputStream

Motivation:
#1939

https://bugs.openjdk.org/browse/JDK-6357433 (in a comment) says:

For jdk7, the workaround is to use new file system API. So instead of new FileInputStream(f) and new FileOutputStream(f), use f.toPath().newInputStream() and f.toPath().newOutputStream()

So seems like new NIO API does use, FILE_SHARE_DELETE, which is needed to delete files in unix-style.

[lihaoyi]

Thanks @sake92! Might need to send a PR upstream to OS-Lib as well https://github.com/com-lihaoyi/os-lib/blob/f1bf225f8b110c4a561465717d8b13efcd9ee6d3/os/src/ZipOps.scala#L75

[lihaoyi]

We also use java.util.jar.JarOutputStream in some places in Mill, I'm guessing that API predates NIO and may need to be updated as well

[sake92]

Thanks @sake92! Might need to send a PR upstream to OS-Lib as well https://github.com/com-lihaoyi/os-lib/blob/f1bf225f8b110c4a561465717d8b13efcd9ee6d3/os/src/ZipOps.scala#L75

Sure thing, I'll update it there too.

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We also use java.util.jar.JarOutputStream in some places in Mill, I'm guessing that API predates NIO and may need to be updated as well

JarOutputStream is not OS-dependent like the java.io input/output streams. I might be wrong tho.
https://docs.oracle.com/javase/8/docs/api///?java/util/jar/JarOutputStream.html says:

The JarOutputStream class is used to write the contents of a JAR file to any output stream. It extends the class java.util.zip.ZipOutputStream with support for writing an optional Manifest entry. The Manifest can be used to specify meta-information about the JAR file and its entries.