opencv: migrate remaining ports; mark obsolete and replaced_by opencv3

[mascguy (Christopher Nielsen)]

While the vast majority of ports have been migrated off of legacy port opencv, there are a few remaining.

In terms of working ports, there is only one:

• auto-multiple-choice: will be migrated to opencv4 when v1.5 officially released

The other dependent ports are failing to build across all macOS releases:

Port	Tracking Ticket	Notes
caffe	​https://trac.macports.org/ticket/62766	Builds failing since 2019 or earlier. Obsolete?
digikam	​https://trac.macports.org/ticket/62755	Builds failing since 2018 or earlier. Also very out-of-date.
objectmarker	​https://trac.macports.org/ticket/58094	Builds failing since 2019 or earlier. Obsolete?
orfeotoolbox	​https://trac.macports.org/ticket/62754	Builds failing since 2020 or earlier. Also very out-of-date.

[mascguy (Christopher Nielsen)]

Updated opencv to include comments, and user notes, clarifying that port is obsolete.

[Christopher Nielsen <mascguy@…>]

In 3a9af39b875853abfb9e758c063de0eacb517bd2/macports-ports (master):

caffe: migrate to boost pg, and opencv3

• Note that this port was/is broken across-the-board; more work needed to fix.

See: #62774

[Christopher Nielsen <mascguy@…>]

In 4f5a282134fae9402eb667c6788409ca53bbda71/macports-ports (master):

objectmarker: migrate to opencv3

• Note that this port was/is broken across-the-board; more work needed to fix.

See: #62774

[Christopher Nielsen <mascguy@…>]

In 26783432c4900ab73e4237ffa89e8c02342f04f5/macports-ports (master):

orfeotoolbox: migrate to boost pg, and opencv3

• Note that this port was/is broken across-the-board; more work needed to fix.

See: #62774

[Christopher Nielsen <mascguy@…>]

In 96a158be108ea09f404155f57ef98b532e90486c/macports-ports (master):

digikam: migrate to boost pg, and opencv3

• Note that this port was/is broken across-the-board; more work needed to fix.

See: #62774

[Christopher Nielsen <mascguy@…>]

In 81fc7338ca1b52b33d237c730169f603a9d41714/macports-ports (master):

auto-multiple-choice: migrate to opencv3

See: #62774

[Christopher Nielsen <mascguy@…>]

In 1d12f474e72eb37313beec9ac57305fff05d7f99/macports-ports (master):

opencv: obsolete port

Closes: #62774