fix(compiler): support one additional level of nesting in :host()

Previously we supported one level of nested parentheses inside of a
`:host()` selector, e.g. `:host(:not(p))`. This caused a breakage in g3
when I migrated a selector from `:host:not(:has(p))` to
`:host(:not(:has(p)))`. This change adds support for just one more level
of nesting.

It'd be nice to move everything to a real CSS parser (or even update it
to count parentheses like I did with :host-context()), but I wasn't able
to get that to work in ~20 minutes and I'm focusing on other things at
the moment.

This change punts the problem until somebody tries to use just one more
level of nesting in a selector.

Fixes #64830

packages/compiler/test/shadow_css/host_and_host_context_spec.ts

@@ -83,6 +83,9 @@ describe('ShadowCss, :host and :host-context', () => {
       expect(shim(':host(:not(p)):before {}', 'contenta', 'a-host')).toEqualCss(
         '[a-host]:not(p):before {}',
       );
+      expect(shim(':host(:not(:has(p))) {}', 'contenta', 'a-host')).toEqualCss(
+        '[a-host]:not(:has(p)) {}',
+      );
       expect(shim(':host:not(:host.foo) {}', 'contenta', 'a-host')).toEqualCss(
         '[a-host]:not([a-host].foo) {}',
       );