tests: constify, make consts static

[vszakats]

• lib509: constify an input string.
• add static to const data, where missing.
• tool1394: fix indentation.

[vszakats]

wat?:

/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:219:10: error: Initialized va_list is leaked [clang-analyzer-valist.Unterminated,-warnings-as-errors]
  219 |   return TRUE;
      |          ^
../../lib/curl_setup_once.h:273:14: note: expanded from macro 'TRUE'
  273 | #define TRUE true
      |              ^
/usr/lib/llvm-18/lib/clang/18/include/stdbool.h:21:14: note: expanded from macro 'true'
   21 | #define true 1
      |              ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:178:14: note: Assuming 'i' is < 'len'
  178 |   for(i = 0; i < len; i++) {
      |              ^~~~~~~
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:178:3: note: Loop condition is true.  Entering loop body
  178 |   for(i = 0; i < len; i++) {
      |   ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:179:8: note: Assuming field 'show' is not equal to 0
  179 |     if(!ctx->show) {
      |        ^~~~~~~~~~
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:179:5: note: Taking false branch
  179 |     if(!ctx->show) {
      |     ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:188:8: note: Assuming field 'show' is equal to 1
  188 |     if(ctx->show == 1) {
      |        ^~~~~~~~~~~~~~
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:188:5: note: Taking true branch
  188 |     if(ctx->show == 1) {
      |     ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:191:7: note: Taking true branch
  191 |       if(!memcmp(ctx->rbuf, ctx->arg, ctx->flen)) {
      |       ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:193:9: note: Initialized va_list
  193 |         fputs(&ctx->arg[1], stdout);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:196:7: note:  Execution continues on line 178
  196 |       continue;
      |       ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:178:14: note: Assuming 'i' is >= 'len'
  178 |   for(i = 0; i < len; i++) {
      |              ^~~~~~~
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:178:3: note: Loop condition is false. Execution continues on line 219
  178 |   for(i = 0; i < len; i++) {
      |   ^
/home/runner/work/curl/curl/bld/src/../../src/tool_help.c:219:10: note: Initialized va_list is leaked
  219 |   return TRUE;
      |          ^
../../lib/curl_setup_once.h:273:14: note: expanded from macro 'TRUE'
  273 | #define TRUE true
      |              ^
/usr/lib/llvm-18/lib/clang/18/include/stdbool.h:21:14: note: expanded from macro 'true'
   21 | #define true 1
      |              ^
make[1]: *** [Makefile:2850: tidy] Error 1

https://github.com/curl/curl/actions/runs/15853995045/job/44694496861?pr=17736#step:33:646

[vszakats]

A bit-flip? it ran fine the second time ¯\(ツ)/¯:
https://github.com/curl/curl/actions/runs/15853995045/job/44696006274?pr=17736#step:33:597