Error when parsing anchor names ending with underscore-number

Anchors generated by FontLab when reading binary font files usually end with underscore-number, e.g. `_t.uni3001_1`. When passing these names generated by FontLab into `fontmake`, the builder fails as the anchor name with underscore-number are identified as the index of ligature component to attach to.

```log
Traceback (most recent call last):
File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 519, in _iter_compile
yield compile_func(ufo, debugFeatureFile=debugFeatureFile, **options)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\ufo2ft\__init__.py", line 117, in compileOTF
return OTFCompiler(**kwargs).compile(ufo)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\ufo2ft\_compilers\baseCompiler.py", line 65, in compile
self.compileFeatures(ufo, font, glyphSet=glyphSet)
File "C:\Python311\Lib\site-packages\ufo2ft\_compilers\baseCompiler.py", line 145, in compileFeatures
otFont = featureCompiler.compile()
^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\ufo2ft\featureCompiler.py", line 148, in compile
self.setupFeatures()
File "C:\Python311\Lib\site-packages\ufo2ft\featureCompiler.py", line 315, in setupFeatures
writer.write(self.ufo, featureFile, compiler=self)
File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\baseFeatureWriter.py", line 151, in write
self.setContext(font, feaFile, compiler=compiler)
File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 325, in setContext
ctx.anchorLists = self._getAnchorLists()
^^^^^^^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 360, in _getAnchorLists
a = self.NamedAnchor(name=anchorName, x=x, y=y)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 177, in __init__
isMark, key, number = parseAnchorName(
^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\ufo2ft\featureWriters\markFeatureWriter.py", line 151, in parseAnchorName
raise ValueError("mark anchor cannot be numbered: %r" % anchorName)
ValueError: mark anchor cannot be numbered: '_t.uni0308_2'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "C:\Python311\Lib\site-packages\fontmake\__main__.py", line 746, in main
project.run_from_ufos(
File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 1374, in run_from_ufos
self.build_otfs(ufos, cff_version=cff_version, inplace=inplace, **kwargs)
File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 315, in build_otfs
self.save_otfs(ufos, **kwargs)
File "C:\Python311\Lib\site-packages\fontTools\misc\loggingTools.py", line 375, in wrapper
return func(*args, **kwds)
^^^^^^^^^^^^^^^^^^^
File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 682, in save_otfs
for font, ufo in zip(fonts, ufos):
File "C:\Python311\Lib\site-packages\fontmake\font_project.py", line 521, in _iter_compile
raise FontmakeError("Compiling UFO failed", ufo.path) from e
fontmake.errors.FontmakeError: In 'orig-pearl-tangyuan-v2.ufo': Compiling UFO failed: mark anchor cannot be numbered: '_t.uni0308_2'
```

This convention is not noted anywhere in any formalised standards, and is only noted in `parseAnchorName()` function description of `ufo2ft`:

> Parse anchor name and return a tuple that specifies:
1) whether the anchor is a "mark" anchor (bool);
2) the "key" name of the anchor, i.e. the name after stripping all the
prefixes and suffixes, which identifies the class it belongs to (str);
3) An optional number (int), starting from 1, which identifies that index
of the ligature component the anchor refers to.
>
> The 'ignoreRE' argument is an optional regex pattern (str) identifying
sub-strings in the anchor name that should be ignored when parsing the
three elements above.

It is not mentioned in [UFO specification](https://unifiedfontobject.org/versions/ufo3/glyphs/glif/#anchor):
> `name`: An arbitrary name for the anchor. This attribute is optional. It must be at least one character long. There is no maximum name length. A name must not contain [control characters](https://unifiedfontobject.org/versions/ufo3/conventions/#controls).

and

> Anchor naming conventions[↩](https://unifiedfontobject.org/versions/ufo3/glyphs/glif/#anchor-naming-conventions)
> The following are agreed upon standard naming conventions for special uses of the `name` attribute.
>
> Ligature Carets[↩](https://unifiedfontobject.org/versions/ufo3/glyphs/glif/#ligature-carets)
> Anchors with a `name` starting with `caret_` or `vcaret_` indicate horizontal or vertical caret positions for ligature glyphs. Example usage would be to compile the [OpenType GDEF Ligature Caret List table](https://docs.microsoft.com/en-us/typography/opentype/spec/gdef#ligature-caret-list-table-overview).
>
> Anchor names starting with `caret_` provide the `x` value for a ligature caret position, and the `y` value is ignored. Likewise, anchor names starting with `vcaret_` provide the `y` value for a ligature caret position, and the `x` value is ignored.
>
> Both names may be followed arbitrary text (`caret_1`, `caret_blah`, etc) for designers or applications to have unique caret position names.
>
> There must be exactly N-1 caret positions for N ligature components.

Or in [AFDKO FEA syntax](https://adobe-type-tools.github.io/afdko/OpenTypeFeatureFileSpecification.html#2eviii-named-anchor-definition):
> The anchor name follows the same rules as are used to form glyph names. For example:
> ```
> anchorDef 300 0 ANCHOR_1;
> anchorDef 120 -20 contourpoint 5 ANCHOR_2;
> ```