LEF parser fixes and Lefrw utility

[nanobowers]

Lef21 enhancements/fixes

• Added lefrw to lef21/bin. This is a simple utility to read a .lef and write it back out.
• Removed ; following MACRO (bug fix)
• Made END LIBRARY optional for lef5.6+
• Added write support for PATH
• Fixed parse of ; after ANTENNAMODEL
• Added FIXEDMASK support for MACRO
• Added ORIENT support for FOREIGN
• Added EEQ support for MACRO
• Added support for TAPERRULE, MUSTJOIN, GROUNDSENSITIVITY, SUPPLYSENSITIVITY, and NETEXPR on PIN

Gds21 fixes

• Fixed bug in gds21 empty.json tests where tests would occasionally fail due to threads using the same file.

If separate PRs per feature of preferred, please LMK.

[dan-fritchman]

Changes look good to me!
Would you mind merging main again to pick up the changes in #49.

[nanobowers]

@dan-fritchman I re-merged with main, shoudl be ready to go.

[dan-fritchman]

Thanks again!