pw_ide: Make activate.py amenable to import
pw_ide: Make activate.py amenable to import

activate.py was designed as a standalone script, but now some if it is
being used elsewhere in pw_ide. This change exposes that functionality
to import, and also cleans up organization and improves documentation.

Change-Id: I6e3377a999134c740c59642efe6b83931450f58b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/112515
Reviewed-by: Anthony DiGirolamo <4cc40125edc24ec5bc72df7917ea0b403ee8cebe@google.com>
Commit-Queue: Chad Norvell <f2b1b54074a2cea3f685a7cf4fc055999c2f0cd6@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed