[Windows] Improve R finding for special installation

[cderv]

This fixes #995

After some tests with R installation with Scoop and rig on Windows, here are some ajustement in what we are doing.
With this change:

• Scoop or rig installation will be found when in terminal for PATH or registry version
• They will also be found inside RStudio where R_HOME is set and takes precedence.

For scoop, as described in #995, the installation will not add a Rscript.exe file in R_HOME/bin, they will be in R_HOME/bin/x64 only. I kept the adjustment simple for now by adding directly the path to x64 folder if none is found in root bin folder. This is really scoped to the specific issue. If we want more generic approach, it could be clever to search for the Rscript.exe within the R_HOME folder and take the first one found. Could be done by refactoring the search in program files

quarto-cli/src/core/resources.ts

Lines 97 to 106 in abb46a3

	// Search program files for the binary
	for (const entry of Deno.readDirSync(progFiles)) {
	if (entry.isDirectory && entry.name === "R") {
	// found the R directory, now walk to find bin directory
	for (const walk of walkSync(join(progFiles, "R"))) {
	if (walk.isDirectory && walk.name === "bin") {
	return join(walk.path, binary);
	}
	}
	}

If needed, I'll add that.

For rig, it took me more time to test because I found a few issues that messed up my system; They are reported in https://github.com/r-lib/rig. It helps though identified one thing: which() uses CMD /C WHERE <binary>. This command on windows will return all the files found, and not just the only one like which on Linux. I added a handling of this: we are keeping only the first path returned.

Regarding search in registry, , I noticed a few things that I was not sure :

• Is there a reason to no read the version install path in two steps ?
  

  quarto-cli/src/core/resources.ts

  Lines 76 to 93 in abb46a3

  	if (Deno.build.os === "windows") {
  	// determine current version
  	const version = await registryReadString(
  	[kHKeyLocalMachine, kHKeyCurrentUser],
  	"Software\\R-core\\R",
  	"Current Version",
  	);
  	// determine path to version
  	if (version) {
  	const installPath = await registryReadString(
  	[kHKeyLocalMachine, kHKeyCurrentUser],
  	`Software\\R-core\\R\\${version}`,
  	"InstallPath",
  	);
  	if (installPath) {
  	return join(installPath, "bin", binary);
  	}
  	}

  
  Software\\R-core\\R as a InstallPath value directly. So I was wondering by curiosity. I did not change anything as this is working fine currently.

• Slightly unrelated, we have two sets of registry reading functions: in registry.ts and in windows.ts. Should we try refactor into one set for easier upkeep in the future ? Asking because I fixed one issue in the past in windows.ts for chrome finding, but not the other that I wasn't aware of.

[jjallaire]

I'll let @dragonstyle comment on the two-step registry reading (but I agree that leaving it alone is best for now in any case).

As far as refactoring registry functions, let's do this on v1.1 (trying to minimize changes that could lead to breakage on v1.0 right now).