build: panic = abort and lto = fat for release

[86xsk]

Issues

Related to #1945

Description

Reduces binary size of harper-ls by about ~7MiB. Both panic = "abort" and lto = "fat" contribute to approximately half of this reduction.

Some rudimentary test results I gathered from experimentation:

Config	Size of harper-ls (MiB)
Current	60.56
panic = "abort"	57.67
panic = "abort" + ThinLTO	57.46
panic = "abort" + FatLTO	53.53

cargo bench --bench parse_essay also shows a ~4.4-11.5% performance improvement across the board.

How Has This Been Tested?

• cargo test
• cargo bench

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes