feat: Support hermetic patching

[LaurenceTews]

Allows Bazel native patch to be used with npm_import(). This removes the existing dependency on patch when enabled. The proviso is that patch diff headers must have an unstripped 'package/' prefix when use_native_patch is true. The dirname 'package' is the de facto standard for npm packages, though this isn't enforced.

Type of change

• New feature or functionality (change which adds functionality)
• Documentation (updates to documentation or READMEs)

For changes visible to end-users

Suggested release notes are provided below:

• use_native_patch flag added to npm_import, allowing for hermetic patching.

Test plan

Manual testing steps:

• set BAZEL_SH var to a nonexistent path.
• Create valid patch. Patch diff header should contain package prefix, e.g. "diff --git package/lib/font.coffee ..."
• verify that npm_import() with patch applied fails "Error applying patch". System 'patch' cannot be found.
• verify that npm_import() with patch applied and use_native_patch set to 'True' succeeds.

[LaurenceTews]

@gregmagolan Just wanted to gauge if there's any interest in this feature? I know Windows is a lesser used platform, but I'm sure there's teams out there (like mine) who would find this useful.

[matthewjh]

@gregmagolan any thoughts on this MR? I tried to run a rules_js project on Windows, and it blew up while resolving NPM packages due to the "patch" dependency.

[smocherla-brex]

Ran into this issue as well on our Macs which have an older version of patch which is stricter than the one on Linux. Would be nice to use the native patch implementation as opt-in as this PR does. (although for our usecase a note in the docs for npm_translate_lock regarding this would also suffice)

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