R1:e1da1d86d680

Trim and URI encode symbol names before building URIs from them

Summary:
Fixes T13437. This URI construction was just missing URI encoding.

Also, trim the symbol because my test case ended up catching "#define\n" as symbol text.

Test Plan:
- Configured a repository to have PHP symbols.
- Touched a ".php" file with "#define" in it.
- Diffed the change.
- Command-clicked "#define" in the UI, in Safari/MacOS, to jump to the definition.
- Before: taken to a nonsense page where "#define" became…