Let Figure.text() support record-by-record transparency

[seisman]

Description of proposed changes

This PR implements the record-by-record transparency feature for Figure.text() function.

Example:

import pygmt
import numpy as np

x = np.arange(1, 10)
y = np.arange(11, 20)
text = [f"TEXT-{i}-{j}" for i, j in zip(x, y)]
transparency = np.arange(10, 100, 10)

fig = pygmt.Figure()
fig.basemap(region=[0, 10, 10, 20], projection="X10c", frame=True)
fig.text(x=x, y=y, text=text, transparency=transparency)
fig.show()

Output:

Fixes #615.

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Notes

• You can write /format in the first line of a comment to lint the code automatically

[seisman]

/format

[weiji14]

Style checks are failing, and we really need to refactor this text function (along with #483).

pygmt/base_plotting.py:1377:4: R0914: Too many local variables (16/15) (too-many-locals)
pygmt/base_plotting.py:1377:4: R0912: Too many branches (13/12) (too-many-branches)

[seisman]

Style checks are failing, and we really need to refactor this text function (along with #483).

pygmt/base_plotting.py:1377:4: R0914: Too many local variables (16/15) (too-many-locals)
pygmt/base_plotting.py:1377:4: R0912: Too many branches (13/12) (too-many-branches)

Yes, let's leave it to future PRs.

[weiji14]

Ok then!