Fix remaining LICENSE files (#3193)

# Description of Changes

Apparently, I missed several license files in #3002. I'm not sure what
method I was using to find them, but apparently it was insufficient.

**This replaces all empty `LICENSE` files with an explicit (symlink to)
BSL license, and all apache licenses with symlinks to the root apache
license.** This PR does not intentionally change any license terms, so
if you see one that changed, **it's a mistake**.

# API and ABI breaking changes

None

# Expected complexity level and risk

1

# Testing

```bash
$ find . -name '*LICENSE*' -type f | grep -v '\.meta$'
./crates/sqltest/standards/LICENSE # this one is an external library that we are not allowed to re-license
./LICENSE.txt # this is the root license
```

---------

Co-authored-by: Zeke Foppa <[email protected]>

Author: bfops

docs/LICENSE.txt

@@ -0,0 +1 @@
+../licenses/apache2.txt

docs/LICENSE.txt

@@ -0,0 +1 @@
+../../licenses/BSL.txt

docs/bsatn/LICENSE

@@ -0,0 +1 @@
+../../licenses/BSL.txt

docs/bsatn/LICENSE

@@ -0,0 +1 @@
+../../licenses/BSL.txt

modules/benchmarks-cs/LICENSE

@@ -0,0 +1 @@
+../../licenses/BSL.txt