v help: add all tool commands to v help <command> (#10419)

cmd/v/help/doctor.txt

@@ -0,0 +1,3 @@
+Usage: v doctor
+
+Display some useful info about your system necessary for bug reports.

cmd/v/help/list.txt

@@ -0,0 +1,3 @@
+Usage: v list
+
+List all installed modules.

cmd/v/help/outdated.txt

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+Usage: v outdated
+
+List all installed modules that need updates.

cmd/v/help/repl.txt

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+Usage: v repl
+
+This command runs the V REPL.

cmd/v/help/self.txt

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+Usage: v self
+
+Rebuild V with the passed options.
+
+Options: All other options are passed to the build command. (e.g. -prod)

cmd/v/help/show.txt

@@ -0,0 +1,3 @@
+Usage: v show
+
+Display information about a module on vpm.

cmd/v/help/symlink.txt

@@ -0,0 +1,5 @@
+Usage: v symlink
+
+This command adds a symlink for the V compiler executable.
+
+Note that on Unix systems this command requires write permissions to /usr/local/bin to work.

cmd/v/help/tracev.txt

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+Usage: v tracev 
+
+Produce a tracing version of the V compiler.

cmd/v/help/up.txt

@@ -0,0 +1,7 @@
+Usage: v up
+
+Update the V compiler to the latest version from https://github.com/vlang/v.
+
+Options:
+  -v           - Print more details about the update.
+  -prod        - Compile the updated V with the -prod flag.

cmd/v/help/update.txt

@@ -6,5 +6,5 @@ Usage:
 
 Options:
   -help        - Show usage info.
-  -v           - Print more details about the performed operation.
+  -v           - Print more details about the update.
   -server-url  - When doing network operations, use this vpm server. Can be given multiple times.

cmd/v/help/upgrade.txt

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+Usage: v upgrade
+
+Upgrade all outdated modules.
+
+Options:
+  -help        - Show usage info.
+  -v           - Print more details about the upgrade.

cmd/v/help/version.txt

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+Usage: v version
+
+Print the version of V installed.